never use 2k etch as a primer! ever! it's only designed to go underneath a 2k primer, or a 2k non sanding primer.
i wouldn't recommend using a non sanding primer for a respray though, it will sink back. just buy a decent quality primer that self etches and leave your car sitting in primer for around a month for best results. i would apply 4-5 wet coats this should give you more than enough material to play with.
as for water filters, i've never needed one, my shop uses screw type compressors with inline water filters. i wouldn't cheap out though, as water in your job is a massive headache.
what do you want to touch up?
i would suggest doing a spot in if its on the edge of a bar or something, if its in the middle of a panel you'll need to paint the whole thing other wise it'll get messy.
spot ins are difficult, if you wanna try id get an old panel to practice on. here are the steps
1. using soft filler (also known as 2pack filler) lightly apply a skin over the scratch and allow to dry. it should only just cover it, if you put too much in you will leave ripples around the area.
2. using p400 dry block the filler flat making sure the the filled area is visible, but with the filler just covering the area.
3. prime with 2 thinned out coats of primer.
4. wet rub the primer with p600 for a solid or p800 for metallic.
5.rub the surrounding area ( around 15cm) with p1200 or 1500.
6. blow of the area and clean with wax and grease remover
7. mask up any area you dont want painted clean again.
8. wipe the area down with a tack cloth. (i recommend a gerson blue)
9. solid colour: apply 2 coats over the primer allowing 15mins for flash off in between coats with the second coats covering a larger area.
metallic: this is tricky, cover the primed area usually will take 2-3 wet coats. if you want to check it's covered properly turn off your lights and shine a torch on the painted area, it will show the primer if its not. next you will need to flick the colour out, this will take some practice. just flick your wrist out and only dust the colour on.
10. tack rag again. (metallic ONLY)
11. apply 2 coats of clear (metallic only) allowing 15mins in between. the 2nd coat should cover the entire rubbed area.
12. using a high quality thinner, or even better a blending thinner, apply a medium wet coat of thinner to the edge of the clear. be careful here as you will get runs if you over do it. which means a repaint.
13. drink a beer and admire what you have accomplished.
Ive got a question for you. I just bought a set of side skirts, a rear bumper and boot spoiler from a VX SS. They are all painted beige at the moment and I obviously want to get them painted to match my car (metallic blue VX). My question is how would i go about sanding back the old paint to the bare plastic (this saves alot of $$ the panel beaters) Im pretty handy with sandpaper and am confident that I can do it I just need to know where to start.
i wouldn't sand it back to plastic, this will require it to be primed, if you wanna just rub it for painting, use p400 on a whizzer or p800 wet by hand. but only if they are in good condition, if they're a little worse for wear they'll need to be primed and rubbed again.
as for vinyl dye i have no idea. it's not an area i have dealt with. sounds like something a trimmer would do. but if you want to paint plastic parts rub with p800 wet or p500 dry by hand then use a plastic primer. protec make one at a reasonable price, then paint away.
i was wondering what the best way to prepare a surface for bog would be. is it ok to bog over old paint, or does it all have to be sanded back to metal? can you bog over hi-fill. and what is the best way of stopping pin holes from happening.
also, on the pin holes point, why is it when i run fine filler over pin holes. it seems like they fill up then the filler lifts out of the holes once the applicator goes past them.