Ok
You need a compressor that will give you 12+-CFM something like 150L 3HP, for small jobs you can go a bit smaller.
Air hose must be no longer than 12m and have no smaller than 6mm inner diameter.
Buy your paint and spray gun at any big reputable automotive paint store.
I use a Devilbiss Pro GTI spray gun but you do not need a expensive gun like this.
For minor repairs: ie scratch that also made a slight dent.
First thing is you wash the area you want to work on with degreaser.
Then use 80 grit sand paper and scuff the damaged area real good.
Then scuff the outer edges of the 80 grit area with 220 grit sand paper.
Now sand the whole panel with 400 grit(for 2k paint) 600 grit(for metallic) with warm water and a little degreaser in the water.
Clean the panel with benzene or something similar after it drayed.
Mix the body filler to manufacturer specs, apply a thin layer of body filler over the area you are working on.
Sand it down with 120 grit and the appropriate sanding block(never sand in one direction, sand at a forward 45 degree and mix up your sanding pattern)
Always feel your work while sanding to help to know what you are doing and what needs to be sanded.
When done then again clean of the dust with benzine or something similar.
Then apply a thin smooth layer of body filler overlapping the sanded filler by about 50%.
Gently sand it smooth with a sanding block and 120 grit paper to the desired shape.
Finish it of gently with 220 grit paper.
Clean the whole panel with benzine or something similar.
Mask of the panel nicely so that over spray does not get onto your car.
Spray gun set up:
You need a pressure regulator on your spray gun.
Pressure regulator on the compressor for the line pressure must be set at 6bar.
Regulator on the spray gun must be set at 2bar while the spray gun trigger is pulled.
Air knob must be fully open.
Fluid knob must be adjusted completely closed and then 1.5-2 turns open (this is a good setting for a noob)
Pattern knob must be adjusted fully open and the spray with some thinners in the gun and adjust the knob
so that the pattern width goes about 10% smaller than max.
Distance of the gun to the panel must be 10/12cm+-
A water/moist trap is also needed on the spray gun pipe.
Now mix your primer to the manufacturer specs.
Throw the primer into the spray gun through a paint strainer.
Again wipe the panel with benzine or something similar.
Apply a coat of primer over the filler, overlapping 50% on each layer.
Move fast with the gun and have a look if you are not putting on to much material.
Wait a minute or two and then put on the next coat, overlapping the previous primer coated area by about 10%
Give it 3-4 coats.
After painted the primer remove the masking.
Let the primer dry real good in the sun for a whole day(important, so that the solvents that needs to evaporate have enough time to do so)
Now you can repeat the wet sanding on the whole panel, but 600 grit for 2k and 800 grit for metallic. Sand it real good!
After it drayed clean the panel with benzine or something similar.
Mask of the panel nicely so that the car is protected form over spray.
Mix your paint according to the manufacturer specs and pour it into your gun throw a paint strainer.
Again clean the panel with benzine or something similar.
Pressure for metallic can be set at 2bar, 2k and clear coat can be set at 2.2-2.5bar.
Spray a fast coat over the primer area and wait 1 minute and spray a fast coat over the whole panel.
Now hit it a bit harder and wait for 2-10 minutes constantly touching the paint (on the masking)
you want it to be tacky and not pull strings when you touch it, when it is nice tacky you can put on the next coat.
Give it 3 coats and study the paint to see if the primer shines through, give it a fourth coat if you feel like it.
Wait 30 minutes and remove the masking and let the paint dry in the sun(paint takes about a week to fully cure)
Give it some polish and you are done.
Never sand filler without a dust mask!
Never spray without a good charcoal respirator!
