I've backed many a limb,all have been glass lams, close to 100 bows done. used to sell a "how to" guide on the auction site. I'm sure the links above give ample info, so just a finish tip.....
Believe it or not, one of the longest lasting bows I have done without so much as an edge lift, a 70" Hoyt Pro Medallist with rattler limbs going on 15 years being backed, has had only Montana Pitch Blend applied once a year. No finish sprayed on over the skins. I finished the bow like all others, leaving the limb backs masked off so no finish gets on them, applied the skins, trimmed, etc, and just pitch blend.
Took it to Newfoundland caribou hunting, constant rain and moisture for 10 days, not the slightest peel. Since then I rarely use any type of finish except leather finishes and oils and it works great. Here are a few quick pics already in photo bucket, cant upload any right now...comp. problems