A french polisher is a man who specialises in the technique of using many layers of very thin polish to bring a smoothly sanded piece of furniture up to a mirror like shine. Which also protects the wood underneath and brings out the grain.

Traditionally the main ingredients of the polish were simply resin and carrying agent- these days you can buy ready made french polish and use a powerdrill with polishing pad attachment to get the same effect. Back for your ancestors this was a method that took a lot of time and elbow grease.

Shellac - this is a resin excreted from an insect from the Indian continent. The resin is used by the beetle to protect larvae, like a temporary shell deposited on the tree. It is a very versatile natural product used in everything from furniture polish to nail polish to food as a glazing agent. In theory the insects aren't harmed by the collection of the shellac, but as the insects hang around the tree where they deposited it, then some adults and all the larvae are killed during harvesting. It's melted down and set into thin sheets, which is then broken into flakes for sale. In it's natural state it has a dark hue that makes the final polish dark, but can be refined with a bleaching process to be lighter or colourless.

Alcohol (Ethanol) - these days denatured alcohol is used, but traditionally methylated spirits (methanol) and other alcohols were used. Obviously this is highly flammable, so no heat is used.

Apprentices (as with painters before paints in tubes were invented) were given the job of dissolving the shellac in the alcohol, shake then leave to rest, then repeat and eventually once the right consistency was obtained and all the shellac dissolved, the mixture would be strained and then used. It had a shelf life of months. The proportions of shellac to alcohol depends on what you wanted to do with it, use it as a primer or a top coat, and over time the alcohol evaporated (air tight containers that could be reopened and resealing being a relatively modern invention).

Before use the mixture must be left to stand so that there are no air bubbles that would disturb the application of the mixture to the wood. The furniture would be sanded with increasingly fine grades and ultimately with filler to make the final surface to be french polished as smooth as was humanly possible.

The mixture is applied with a pad not a brush. And the pad is oiled to aid the smooth application. The first coat raises the cut grain of the sanded wood but if it's been properly prepared in the first place, this enhances the organic 'polish growing out of the wood' sense of depth as the subsequent layers of polish don't raise it further (hence using alcohol not water as the carrier). The Victorians will have used oils easily available to them, linseed for example to prime the pad.

Each layer of polish would be applied in a particular pattern in a particular order favoured by that craftsman. Maybe first up and down in rows along the grain, then in a series of circular motions for the next layer and so on, this prevented 'ridges' of polish building up. Each layer is very very thin, and once applied (in a dust free atmosphere if possible) is left to dry and cure before another layer is added. As each layer is added, the craftsperson adjusts the amount of oil on the pad, and also the amount of alcohol added to the polish mixture to control the flow of the polish and the speed of drying. With shellac being a natural material, it is affected by environmental changes such as humidity or heat etc. Done properly there ought to be no need to sand shellac layers before applying the next.

The number of layers determines the finish, whether it is matt or gloss, it can be so glossy that it is reflective. And again a skillfully and properly applied french polishing wouldn't have required much actual polishing with a cloth after the last layer, which is always very lightly done and with the grain.

Obviously the manhours and skill involved in covering furniture with up to 30 layers of shellac, is enormous, even at a time when labour was cheap. This was a process that only the rich could afford, the craftsman himself couldn't afford to own pieces of his own work (as was common at the time). And trying to keep a dust free atmosphere in a victorian urban environment must have been very challenging.

It is also a very expensive finish to maintain, it is not waterproof, and even a tiny drop of water seeps into the finish and turns it a cloudy white, which needs sanding back and refinishing the whole surface of the piece, not merely the cloudy part.

Naturally it was used only for the most exotic/expensive woods with grains that were enhanced by it, generally hardwoods such as mahogany and walnut, which are often dark as shellac is dark.

Ordinary people's furniture in Victorian times and earlier was either covered by cloths to protect them, or made of less fine woods which could be scrubbed. So for example, a family may have a piece of french polished furniture in the parlour, which was used rarely, but a deal table that could be scrubbed in the kitchen.

In historical terms, Georgian & Victorian (UK Kings) period, of the 1800s onwards was the prime period of popularity of french/pad polishing.

It wouldn't comment so I split it - this is part one.

This may underperform the subreddit's requirements slightly--I leave it to the moderators--but one reason to be cautious as you are being here is that assumptions about what titles in the past might mean in technical terms are a huge danger in historical research even into the relatively recent past. This was the issue at stake recently in rebukes to the author Naomi Wolf on her new book about sexuality in the 19th Century in the UK--that Wolf misread a phrase in legal decisions that meant something very different than what she commonsensically thought it meant. (A good primer on this conversation.)

So take "French polisher", a phrase that the rest of Reddit would very very much enjoy and make out to be something it's not. It really is just an artisan involved in a very difficult, high-end, labor-intensive process of finishing high-quality furnishing. Your relative's reputation is in this case perfectly safe. Horsehair manufacturer is equally soothing: haircloth was often used in high-end tailoring in the 19th Century (generally for men's jackets), and probably for other high-end artisanal tailoring, I'm guessing. "Bird dealer" I can't speak to but I'm guessing (if the mods don't mind) that it is not a euphemism for something slightly risque. Not the least because family trees don't ever, ever indicate that anyway if they're drawing from the census. The census did not (still doesn't) record euphemisms for illegal or intensely informal professions, in Europe or the United States. A historian who suspects that someone they're studying was involved in something of the sort will have to look somewhere besides a census (or a family tree drawn from such).