A few things I've noticed, from working "paint prep" at a couple body shops...
1) Anywhere you need to use a filler, try to use a metal filler. If you're going to go with black, it's going to soak up heat - and that can make Bondo fall off. I prefer a filler called "Metal2Metal" - sometimes called "AllMetal" - it's a two-part putty like Bondo, but it's a metal putty instead of a plastic. Save plastic for filling plastic. Remember that most body fillers tend to shrink as they cure, and require extended curing times. You should also be able to build-up the fill area with thinner layers, which will give a better finish.
2) Preparation is key. Use Rust-Mort for rust spots (should be able to find it the same place you find AllMetal,) and do your prep sanding with about 180 grit paper - using a Dual-Action (DA) orbital sander, if you can get one - that reduces toolmarks.
3) After sanding, go over the entire vehicle, and any small imperfections should be filled with "glazing putty" - which is thin enough to work for this. Regular body filler of pretty much any variety won't do the job - it doesn't get into the cracks. Filled spots should be checked especially well.
4) After you finish sanding - and right before you paint - wipe ALL surfaces down with a solvent - denatured alcohol, acetone, or methyl-ethyl-ketone are all readily available and will work well. As you are doing this, DO NOT TOUCH ANY SURFACE with your bare hands or with any dirty glove - or you'll have to wipe the area down again. You're doing this to get rid of any residual surface oils, sanding dust, or finger oils. Use lots of paper towels for this, and you can burn them in a coffee can afterwards to get rid of the solvent.
5) Remember, the area where you're going to paint should be free of dust and drafts - a clean garage is best. Wash down the floor if you can, sweep it and blow it clean if you can't. You can't get this too clean - most "pro" spray booths I've seen have large-bore hoses and high pressure to spray down THE ENTIRE BOOTH - and all electrics are sealed against water intrusion.
6) If you're going to work in your garage, have the door open about a third of the way, something open at the other end, and have a fan blowing under your truck. This will help to keep fumes away from you (paint is heavier than air, and you've created a draft that will help get them out,) and you'll probably want a mask anyhow. If you start to feel at all lightheaded or "goofy" - GET OUT. RIGHT THEN AND THERE. Once you are outside, check your fingernails - the tissue under them should be pink. If it's white - or doesn't turn pink right away after you squeeze them for a second, STAY OUTSIDE for at least an hour - you're oxygen-starved and need to breathe clear air. Take a break after every major panel for about 5-10 minutes - most "spray-bomb" paints are formulated to work with that.
Why did I not tell you to open the door all the way? One stiff breeze, and you just tripled your work. By keeping the door mostly closed, you keep out breezes, By putting that strong fan blowing across the floor, you have created ventilation - but it won't interfere with your work. Monitor yourself closely - hypoxia is no joke!
Most clearcoats are either gloss or semi-gloss - if you don't use one, preparation will become CRITICAL. If you're going to clearcoat, use a gloss or semi-gloss paint to match - otherwise, it looks silly. I'd suggest two primer coats, two colour coats, and two clearcoats (it's formulated to protect paint
or three primer coats and four colour coats. I'd not expect a rattle-can to give me good one-pass coverage - the volume delivery isn't like what you'd get with an HVLP air sprayer. Pay particular attention to the rocker panels and other lower surfaces - that's where the "salt cancer" will usually start.
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