What is the tradition called where men, often before battle I've noticed, would blow there nose, wash there hair and face in a bowl of water and then pass it to the next man to do the same? What was the significance for this and why did the Norse continue it long after the Germans did?
I think you may be a little confused, possibly from having seen such a scene in The Vikings TV series. This practice was reported by Ahmad ibn Fadlan, who traveled as part of an embassy to the Bulgars on behalf of the the Abbasid caliphate in Baghdad in the 10th century. Along the way he encountered some of the Rus', Norse who had settled in the East. ibn Fadlan disliked the Rus' immensely and provides many lurid details of their daily life, though there's good reason to think much of what he said is exaggerated, as it's not correlated by any other information. The episode with the wash bowl, for example, may have been embroidered by ibn Fadlan as it clashed with his Islamic beliefs, which mandated washing in running water: even though the Rus' probably emptied out the bowl between uses (because let's be honest, not doing so would be gross,) ibn Fadlan would have still felt the practice of washing from a basin to have been unclean. Our other sources record the Norse as having generally been pretty tidy by the standards of their era: the modern Scandinavian languages' names for "Saturday" actually mean "washing day," for example, and we have sources complaining that the Norse spent too much time washing themselves and attending to their hair. It would seem ibn Fadlan strongly exaggerated his description of the filthy, heathen(!) Rus'. Despite his pretty obvious biases, though, ibn Fadlan's account of his travels and interactions with the Rus' is fairly light reading and very interesting; you can take a look at it here.
To the best of my knowledge, no similar episode is recorded in regards to earlier Germanic folks. I believe the Romans got a bit sniffy about the Celts' practices of treating their hair with lye, or the Germans' beards and tied-up hair, and the Romans regarded the barbarians' washing themselves with soap instead of olive oil as weird - but there's nothing I'm aware of regarding sharing a wash basin in the fashion ibn Fadlan describes.
'What was the significance'
Brotherhood
'why did the Norse continue it long after the Germans did?'
Germanics do not equal Germans (ie; there are nations like the Netherlands and many different parts of nations that were settled by Germanics that aren't Germany).
Christianity came earlier to Germania Superior than it came to Scandinavia.
'often before battle I've noticed'
You were there?