can you press a spray can nozzle? Then yeah, patients is all you need. Spray in thin coats, numerous times, and allow time for paint to flash, or become dry on surface between coats. Thinner coats adhere better, don't run, resist chipping and scratching better, and leave a smoother finish.
When painting anything plastic be sure to sand the surface THOUROUGHLY, and use a special plastic adhesion primer, it'll help you alot! If you are painting over paint, simply scuff the existing paint to a no shine finish and lay paint overtop. If you have any repairs, like on a bumper, sand the ENTIRE THING, fill nicks or chips with puddy, sand clean, PRIME over the filler, sand again, and paint. If you do not lay primer over filler when something is mostly painted you will get "mirroring" which is where some of the colorcoat will sink into the filler leaving a dull and slightly different colour in that location, and it will look worse then leaving the chips there in the first place!
Also be sure on andthing bare plastic to clean this off before sanding with a tar and grease remover. The bumper may look clean, but when they are manufactured in a mold they spray mold release in first, which is basically grease. This helps them get the bumpers out after they are hardened in the mold. If the bumper was not painted immediatly, or you bought aftermarket parts they most likely will not have taken this first step in preparing the bumper for finish.
