[SLAYTANIC_1134]

Lookin' pretty good.
1. No specific order. Do whatever intrests you, next(interior, suspension, engine.)
2.yes, must sand, and sand again, w/ higher grain sandpaper each time; paint can never be "too" smooth.
3. most two part epoxy's you can smooth w/ your (wet) finger while the epoxy is still soft.
putty on the other hand is a different story, there are so many different kinds. Some putties can be smoothed out and some just clump up. Do not use water to smooth squadron(green)putty, if you have to use it just let it dry, sand and smooth with spot putty. I quit using squdron because I would always have to putty pinholes in the squadron.(why putty, the putty?!?) Tamiya makes great putties & epoxies that are fairly easy to make smooth. Hope this helps.

p.s. what model is that? I've been looking for a c/k chevy dually!