anyone ever paint there plastics ?

Well I know the plastics on my blaster where painted when I bought it. It look like sh*t. The only real painting I've seen on quads is air brushing, but that's of images or decals, not a flat color. I will tell you air brush paint jobs are sweet, but very expensive.
I have all the equp. to paint it just not sure what type of paint . I know it is done all the time . & I am sure painting would be cheeper than byeing new plastics . I know it would take alot of time to prep. & all but thats what makes it a " custom " bike anyway right
The best paint i know of is sikkens. Thats what all my parts on my bike are painted with. Sikkens is high end automotive paint and when used with a clear coat looks great.
Use Fusion paint it works great glossy is REALLY Glossy though just so u kno it does look great all u do is sand it so their is no primer needed just very light coats and let it dry should take a day or two but it's worth it trust me and it won't scratch for rims get mettle primer and mettle paint
Fusion is suppose to be the best plastic paint around. Ive heard it many times over. Ive never used the stuff myself but have seen pictures of what someone claimed was Fusion and it looked sweet. As for strength I heard if painted correctly its great.

So maybe your son did not paint it correctly, also I belive they recommend plastic primer. Theres also many steps involved in painting plastics. sanding, primer, sanding, primer, painting, sanding, painting, sanding, painting, sealer 2-3 times.
I airbrush my takes a while if you arent careful, and you make a mistake in doing the have to rough it up with sandpaper and do it alll over again...but if you are going to have it done nicely...take it to a professional..or if you live near me...bring it to me, i will redo for the same price over and over again without charging for each try until it is right lol. but i used sikkens on my banshee..i airbrushed...and was ticked cuz it took 4ever lol.
What do you have to have to paint the plastics? Like a paint brush wont work right?

nope, paint brush will not work. At least not how you want it to work, ie. not leaving streaks.

plasti-coat and fusion are both arisol cans. Air brushing uses a special setup, small air compressor and airbrush paint kit and special paints. automotive paint ususes large air compressor and a automotive spray gun.
To prep your fenders for plasti-kote you need

Rough grit sand paper
Smoother grit sandpaper
wet towel
your paint of the color you want
can of clear coat

Ok so you take an sand your fenders down with the rough grit to take all the shine away, then you take the smoother grit an you sand it all down good to make the fenders smooth, then you wipe it down with a wet towel an allow it to fully dry, after that start spraying light coats of paint on it should take you like 4-6 times to get the fenders fully painted after the paint drys apply a thick coat of clear coat an let it dry completely.
I don't have any step by step pics, i do have pics an these pics are from 7-8 months after i painted them.