Best thing you can do is paint the car in Etch prime. NOT from a pressure pack, but some of the best quality stuff you can buy. Make sure it has a zinc constituent in it. This helps rust prevention etc.
Make sure you prepare the car BEFORE the etch primer goes on. Sand all metal/painted areas with 800 grit, or a "3m Clean and strip disk (or similar)
Remove ALL surface rust with the strip disk.
You can leave the car in etch prime for ages, just as long as you keep it dry and sand the living daylights out of it so the primer you use before painting can stick to it. You don't have to sand it off, just rough it up.
around 3 to 4 litres of etch would do the car shell (with NOTHING on or in it). and maybe a bonnet, guards, boot, doors etc, just leave them in paint as long as you can until you are ready to paint them. I think for the whole car around 6L should do it. Just buy 1-2L and go from there if you are just doing sections. It's always better to have not enough paint than too much. As over time the paint can go off, and mixing it takes ages!
If you don't know what sort of paint was on it, I'd suggest removing it. Some acrylic paints don't like 2K primers, and vice versa. Try not to mix the paint types as they don't bond well together. My suggestion is to use 2 pack all the way. Make sure you are using a respirator though, as the solvents in 2 pack epoxies are quite nasty.
I suggest you also paint the insides of the chassis rails etc as much as you can. Don't use any wax/fish oil until you have put the final coats of primer on and in some cases the final coats of paint.
Don't put ANY body filler on
non painted metal. Make sure you prime the painted section first, then apply the body filler. The same goes with the body tar/ body deadener. I prefer to use the "2 pack epoxy" style body deadener. It is harder, and stronger than the tar/bitumen based body deadeners. You can spray this stuff using a normal spray gun, but it does take a while to build up the required thickness. (a couple of coats does wonders)
Just buy a cheap shitty spray gun for all of the prep work. For the final coats, either get someone with a booth, or make sure it's a perfect day with no dust/wind/bugs and mates to touch the paint
Shitty guns are great for prep work. You still clean 'em after use, the finish of the primer doesn't matter as much as you sand the crap out of them anyway. Same goes with spray putty.
For the final coats of paint, use a good gun, and a booth.
You probably already knew all this, but it's good to explain just in case!
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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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