Duke used vinyl dye spray paint on the CPS1500 which I now have. Apparently it 'seeps into the plastic when sprayed on, so the colour actually stays there and won’t chip off'. He made a page about it
on his site.
Having this blaster myself, I can confirm, the finished product looks great, AND hasn't flaked, chipped or washed off.
I've done a few detail tweaks with permanent marker, and black tape, which I'll probably post as part of the 'CPS1500 overhaul' thread, which I'll create when I'm finished the... well... overhaul!
Cover anything you don't want covered in paint with masking tape, balloons etc. (be inventive!
), especially the pump or nozzles. If you strip the whole thing down, you can paint just the casing without risk of getting paint in the pump or nozzle components.
For stripes, use strips of masking tape and the spray paint.
For the dragon detail, a stencil and spray paint would be the easiest, and probably give the best result. That, or you buy a waterproof sticker (some sellers on ebay will make any logo you give them into a waterproof sticker!).