The first thing you will discover about real rawhide same' is that it is HARD. You won't be cutting it with a knife or scissors. I use the metal cutting band saw. A pair of sharp bladed metal snips will cut it to trim to shape, but it takes some force. I have broken a pair of snipper handles cutting same'. When soaked in warm water for several hours to overnight it cuts a bit easier.
It sands well with a 120 grit belt for fitting the fuchi and kashira.
Tapering the same' where it will overlay makes the best joint. You sand 1/2" of the inside edge in a tapered edge, and wrap around the tsuka while wet. Bind the whole tight with cord ( paracord works well). Let dry for several days. Take off the binding, mark the cut for the outer edge, unwrap and trim the edge just a tad past the mark. Resoak to make pliable again. Apply the glue to the tsuka, re-wrap the same', wipe off any excess glue, re-bind handle tightly, and let dry for 4-6 days. Un-bind and let dry for a few more days. Sand the overlap joint smooth. I have used Tightbond II as well as Eco-flo leather weld for the glue. I prefer leather weld. If you are a purist, get out the mortar and pestle and boil up some rice.