been following your recent work, love what i see, real nice, it ll be worth the work. i was thinking for one thing, when i get to bare metal, i like to use that 301solution, even if in some situations you get most of the rust off, or you get down to bare metal, mix301 properly, i put in spray bottle, and dose to all metal, after washing off, metal now has rust-resistance, light,small amounts of rust are usually neutralized. another thing the solution does, as i hear, is help the 1st coat of paint(primer) to adhere to metal.
another thing i was thinking, undercoating,rust-proofing/sealing,&sound deadening. the doors, inside, take some, the sound deadening helps there alot. keeps the doors from rattling and carrying road, and metallic sounds. one my one mk2 the sound, fire resist cloth under hood was coming apart, took it off, lot of difference in sound there. just in doors when you finish(if you proof,etc)make sure drains are cleared. the undercarriage has special difficulties, from under fenders, down floor(s), trunk, etc, has to be able to resist, weather, and take a bad beating for as many years as you can get out of it, check and work on it, reapply, periodically. when you get to the end of rear floors to trunk is an especially difficult area to get it all. inside the floors is also quite difficult, being they are down, anything, &water will just sit there. the factory rubber coating,sealant, after so many years,; in mine after ooh, 20years, 25years whatever, a good layer of moisture just sits under the coating. then again it appears the factory from bare metal applied this rubber coating, so anything(water)that gets under coating, well, ive had some work vs.rust, at times. this coating after these years, for me, will just, with a little start, peel off. so something here that adheres to next layer, for you it looks like paint, and keep moisture from getting inbetween. of course here, and undercarriage sound deadening is very pleasing. the sound deadening smooths ride noises, also loud engine noises, body creaking, noises, etc, and can keep your cabin pleasing, not being annoying for people, not getting headaches, etc, keeping noises where you can be social, and not fatiguing driver and passengers. when i took up the rugs(in my older), there is, under the carpet, those particle,board pads, by the time i got there, they about came apart coming out, just thru them away.