Hi, I work for a body shop supply store and you have an alternative method of painting the plastic, painting plastic with a spray gun is not neccessarily the way to go be cause the paint you should use for plastic trim or bumpers is the exact same paint you use, you can buy in a spray can that is made specifically for automotive use and is OEM approved. It is made by SEM and comes in a variety of colors, alot of the body shops we deal with use it with good results, however like any good paint job, the prep work is the key to success, before any sanding clean the plastic first with a good grease and wax remover, then sand with 600 t0 1200 grit sand paper depending on the surface you are painting, after sanding clean surface again with soap and water and blow out any moisture, then use a plastic adhesion promoter such as "bulldog" and then paint! If you are set on buying a spraygun a cheap one (under $75.00) on ebay is fine for your needs, the expensive ones are made for pro painters who need one that will last and replacement parts are readily available, the atomization may be better but for the average person you won't know the difference. Hope this helps