First be sure to clean the surface with a grease and wax remover and then lightly scuff the surfaces to be painted with a scotch brite or similar pad. This will provide the mechanical bond you require. Your base coat should be Auto Air sealer white or dark depending on the color scheme. Full coverage should take three light coats, no less or it will be too thick. You don't need to heat set Auto Air but it will dry faster if you do.
You should use the new Wicked Colors or Auto Borne paints from Createx as they are formulated for that purpose. Actually I highly recommend them anyway as they atomize extremely well due to the higher solvent content and especially when reduced with their 4011 reducer.
To clear coat apply a light tack coat, wait the appropriate flash time and then apply another two medium wet coats allowing sufficient flash time in between.