Over the last several months, I have been trying to get a ton of body work done. List so many things, it didn't look that big when I started. Now, though, its become an ordeal, and Memorial Day is approaching. Preferring not to cut too many corners, I prepped the interior well, but used cheap paint to get 'er done.
Grind, Mama, Grind
In Learning As We Go, I described the state of the steel floors. I won't put sticky-rubber on top of a horizontal steel surface again. I have spent many hours grinding the resulting rust down. I removed all of the interior bits, pulled out all of the McMaster-Carr rubber stuff and set to eliminating all of the rust I could find. There wasn't that much, but I made some discoveries along the way. For example, it looks like there was a brake fluid leak before I owned the bus, and that caused some steel issues behind the driver seat. There are new panels welded in there. Unfortunately, the welds have started to rust, as have the replacement panels, so they got ground down like the main floor did.
I also looked for and found some rust spots that had evolved into small holes on the outside. I ground them out, banged on them with a rubber mallet to shake bits loose and ground some more. Like the floor, I double-coated with NAPA Rust Converter (forcing it inside the holes as well) to stop the cancer from spreading.
Sand, Patch, Sand
Lab Metal that GratefulEd turned me on to. Its a silver putty that dries and sands like body filler, but actually has aluminum in it. Anyway, I had lots of tiny holes in the interior from different interior configurations, multiple window treatment attempts, etc. The Lab Metal applies very easily with a putty knife, and dries very quickly. Keep the lid on your can, or it will dry out on you. I have added paint thinner to my can to keep it extra thin. I've gone over all of the holes in the bus with that stuff. The little rust holes? Gone. The tiny dent near the radio antennae? Gone. It dusts down with sandpaper and patience. Like any other filler (be it Bondo on your car or Spackle in your house), don't over sand, or it will be concave, nullifying your effort.
Vacuum, Wipe Down
Once the holes were filled, and the Lab Metal sanded down, The entire vehicle has to be vacuumed. This took me back to when I used to paint houses. The basic rule was: if you're going to put paint on it, the end of the shop-vac must go across it. Extending that to also include vacuuming anything that was up against where you were going to paint, I ran the duster end of a shop-vac on every inch of the painted bodywork, inside and out. The only thing I didn't vacuum was the ceiling.
Once vacuumed, every inch needs to be wet-wiped with mineral spirits, In cases where there is more than just dust, the surface must be rubbed clean. Like the vacuum, every inch that will receive paint must be wiped down.
Finally, after all that, you're ready to paint. There are lots of options, and few of them are very good. There's the internet-rumored $50 paint job using hyper-thinned Rustoleum. I tried it on my pop-top and bumpers. It doesn't take getting bumped very well. You can get rattle-can Rustoleum, but that has the same problem plus you have airborne paint so you have to protect everything you don't want painted. You can get one-stage enamel. While it is probably possible to apply it without a spray rig, it won't be easy, and probably won't look very good. Once you get to this stage, you're looking at someone with some skill shooting it. You may as well go for the 2-stage, multi-coat job and spend a few grand on it. For my interior, I went the completely other way. I cringe as I write it (as you will as you read it), but I got basic Home Depot Behr interior enamel and color matched it to the foam headliner I'm planning to put in.
...pausing for effect...
Then, T and I got into painting overalls and brushed in the interior. It looks fantastic. Today. I know very well that it will not stand up to getting bumped, and I'll scrape something when I put the interior back in. I don't care. It takes me less than 30 minutes to empty it by myself, and I don't mind doing touch-up whenever things get scratched. Total paint cost: <$30. After driving around in a seemingly Dalmation themed interior (white with black rust-treatment spots all over it), gray with scratches is a major improvement.