I size the bow while the rawhide is soaking, then it has time to dry some before I put the rawhide on. I like it to bee just tacky, not so much that it sticks to your finger, but just so you can feel it's not quite cured. Then I apply glue (TBII or III) to both the back and the hide, after the hide has been wiped as dry as I can get it, and lay it on the bow. you need to be sure to wrap it with something, string, innertubes, or that stretch wrap stuff. Always pull the hide in the opposite direction you are wrapping or it will want to lay itself around the bow in the direction you're wrapping.
If the rawhide is thin enough and you wrap it well you can get it to lay down in, on, around all kinds of knots and dips and twists.
Mark
p.s. some guys hate the process of backing with rawhide but to me it's easier than backing with anything else.