What are the best materials to use for your rest and plate?
I wouldn't say it's the best, but I used to use calf hair exclusively. I use seal skin now and that lasts a bit longer. A buddy of mine uses Cordovan leather and that stuff lasts a long time. The soft side of velcro seems to be popular too and it's cheap for a lot of it.
I was told by 3rivers seal skin wasn't avalable anymore. Where can I get it?
You can no longer get seal skin.
Bear hair and the leather plate. They last for years and you get enough hair to use two or three times.