what is the best way to use hardware store spray can paints? Which for primer, type and finish (flat, semi and glossy?) do i need to use a "paint for plastic" such as Krylon's "Fusion" when painting directly on plastic. If so, can i use Fusion for primer and then other "non-plastic" (e.g. Krylon paints other than Fusion) on top of Fusion. Am having problems with Testors spray paints and hardware store paints are much less expensive> Thx