I rehydrate the skin before gluing it down. That way the skin if more flexible and it lays down on the contours of the bows back and it accepts the glue better. Depending on how thick the skin I sometimes use a wrap but with copperhead and some western D backs no wrap is necessary because they are thin and lay well without it. I do size the bow with thinned TBIII, let it set then glue down the skin by adding glue to both the skin and the bows back.
When I do wrap a skin I remove the wrap after about an hour before the glue sets completely. I do rough trimming with scissors then and remove air bubbles or excess glue pockets while the glue is still somewhat wet. After the glue has cured out completely, generally after 24 hours, I'll go over the raw edges with a smooth bastard file to dress it then fine emory cloth before adding a finish.