You don't prep with adhesion promoter....you prep with well....prep...

.... on plastic you would use soap and water first to get rid of anything that is water based....then use plastic prep with a grey, 3M Scotchbrite pad 3M.7448 ... then spray the adhesion promoter (Bulldog), leave it wet and go straight to paint.
On bare metal prep with metal prep or, if you want to be cheap; rubbing alcohol. Etch prime the area then paint. If not bare metal or prepainted/primed piece then just scuff with fine sand paper and go to paint.