Finally, some updated pictures.
The process is going like this:
Start with the top (sand, repair, repaint). Status: Done
Fix cargo bin (I like to sit in it at shows, so it need to be reinforced). Status: Done
Start at the front of the bus and work to the back (sand, repair, repaint): Status: Front Done!
Also I repaired and significantly reinforced the area around where the spare wheel is mounted. The sheet metal is just really not strong enough to handle the tire, and tends to dent or compress when exposed to any pressure. So I found a big 1/8th inch aluminum road sign on the side of the road, and cut it to fit across the front where the tire goes. I riveted it in place, filled any gaps behind it with expanding foam, then sealed it with Lab-Metal (a liquid metal that dries into solid aluminum). The area is now significantly stronger and will not rust.

Sanded and reinforced

Primed

1st coat

Finished! Thanks to Paul for the bumper trim idea.