Well, your going to get a billion answers, so here mine. I've been using 40 or 60 grit hook & loop on an electric DA sander with my angle die grinder for the hard to reach places. As I get close to metal, I'll switch to 80 grit.
I've been using Evercoat Rage Premium Lightweight, and I like it.
And I've been giving everything an epoxy coat from Southern Polyurethane. LOVE IT!! Can't beat the price, either.
http://www.southernpolyurethanes.com/