The leather tends to be a bit springy so it wants to move rather than be cut. The result is you can feel the leather raised slightly above the wood. Keep the chisel very sharp and take very light cuts when you get to your final shape. You can also attack this with sanding. Before I start sanding, I use 120 grit to sand along the ridge to help knock it down. Otherwise, it turns just fine.
I don't use any special technique or tools. In fact, I use a roughing gouge start to finish on almost all my pens.
Just a standard CA finish. This one has 3 coats with wet sanding from 1500 to 12,000 after each coat.
Glue was my question. I needed something that would bond equally to both leather and wood. I found a glue at Hobby Lobby that claims to bond to anything. Seems to work fine for leather to wood.