The trick to this is getting a supple leather that stretches fairly easy. Cut it out a half inch longer, then wrap the leather around the grip using spring clamps to hold it while you stretch it to fit the grip.
once it's fitting around the grip well mark it top and bottom and cut each side with a straight edge with about 1/4" gap. then use an awl, or a leather punch to your stitching holes evenly about an 1/8" back from the edge of the leather.
when you've got it all cut out and your holes punched, put a little bit of Barge cement on the belly side of the grip and a bit more on the sides. you want to have everything ready to go before applying the cement. you'll have about 30 minutes of working time before it starts setting up good.
when stitching it, use a sinew or heavy waxed thread and get two needles. start out with about 2 feet of sinew.... you'll figure out a good stitch you like the looks of.
it takes a little practice, but it's not all that tough to do once you've done a couple. i think i like the deer & elk hide leather the best.
hope this helps. If you don't have the right leather, or it's too thick, you'll pull your hair out trying this. Let me know... i can send you a piece of this deer skin i like so much. kirk