One important thing to point out about tar & feathering. The idea wasn't necessarily to injure or kill the victim. To quote Gordon S. Wood "But always the aim was to get the suspected persons to recant their former ties to the crown and to reintegrate them back into the community" ^1

Tar & featherings were generally done at night time. This was for partial concealment of the guilty parties but mostly because people worked during the daylight hours. Here's an example of the most infamous tar & feathering case in colonial Boston history. The victim was John Malcolm who was a Customs official living in Boston. He pursued his customs duties with unusual zeal and as a result was generally despised. In fact, this was not his first experience with being tarred & feathered! In 1773 he had a run in with a mob of sailors in Portsmouth, New Hampshire when had informed on a vessel known to smuggle goods. A crowd of about 30 sailors had "genteely tarr'd and feathered" him as the Boston Gazette reported. This consisted of doing the tar & feathering over his clothes, which was in essence a warning to cease his activities.^2

He wouldn't be let off so easy this time. On the night of January 25th John Malcolm was walking down the streets of Boston when George Hewes (the subject of the book "The Shoemaker and the Tea Party") saw him about to strike a small boy. Hewes stopped the Malcolm from striking the boy and Malcolm said that it was none of Hewes' business to be meddling with a gentleman, whereupon Hewes replied "At least I haven't been tarred and feathered". Malcolm then struck Hewes with his cane so hard that it left a gash deep enough to require stitches. Hewes would require stitches and bear the scar the rest of his life (incidentally he would be treated by Dr. Joseph Warren--who would serve as the first President of the Continental Congress and who would die in the closing minutes of Bunker Hill).

Hewes went to the magistrate to get an arrest warrant sworn out, but that night a mob formed outside his home trying to get in (it didn't help matters that Malcolm had continually antagonized the crowd as they gathered outside his home, including at one point stabbing a man in the breastbone with his sword). The mob forced its way in to his home. As he and his family retreated to the second story some men ran and grabbed axes and ladders to force their way in.

The mob eventually won their way in and stripped him to his waist (dislocating his shoulder in the process). They applied tar & feather to him in front of the Customs House, and then pulled him on a sled through town to the Liberty Pole. At the Liberty Pole they put a rope around his neck and threatened to hang him if he didn't apologize and repudiate the governor. He refused to do that. At that point he was beaten with a pole. They then beat him with a rope or whip and according to one account even threatened to cut off his ears. (By this point the tar on his body had frozen into a congealed mess.) Finally he agreed to do as they asked, but they weren't done with him because they continued to drag him through Boston.

This was all done despite George Hewes asking the crowd to wait for arrest to be made. Malcolm was finally dumped at his after midnight--his journey had started shortly after 8pm, so he had endured abuses at the hands of a Boston mob for close to four hours.

The incident would leave him bed-ridden for eight weeks, but he wouldn't die despite it being the worst tar & feathering episode in colonial history. Most of them were like the first episode in Malcolm's life where he was tarred with his clothes on. Some people were tarred with brushes which further reduces the danger and pain levels. ^3

1.) Source: Radicalism of the American Revolution by Gordon S. Wood

2.) Source: The Shoemaker and the Tea Party by Alfred Young

3.) Source: Bunker Hill: A City, A Siege, A Revolution by Nathaniel Philbrick

If you had made enough people angry, whether you were a public nuisance or a public servant (or both at the same time) being tarred and feathered was a public form of humiliation. So you would be stripped to the waist (usually) and pine tar (the stuff used to fill the cracks of a ship) would be applied to your skin. This would cause burns on the skin (to the degree of which I do not know, ask medicine?) anyways, it was very rare that it would go below the waste, or cause serious medical problems. You would then be feathered and paraded around town by the same mob (the point of public humiliation was that people could identify you) So most likely your face would not be feathered. Once everyone had their laugh, and you had experience a good amount of pain and humiliation (you might be beat up some as well) you'd be left wherever the parade ended and getting the tar off would be really painful once it had dried.