If the Trailer is clean,meaning no surface imperfections you dont need to prime it.A couple of coats of sealer used wet on wet with your base coat will work just fine and save you hours of sanding.How you prep raw plastic is very important.DO NOT sand it with 400.Plastic is not the same as a primed part and anything courser than 600 wet will cause fine burrs to rise leaving you with a hairy mess.
Bulldog does make a paste designed to be used with a grey scuff pad{equal to about an 800 grit scratch} on raw plastic that will work quite well for this project.Plastic relies more on a chemical bond rather than a mechanical bond {sand scratch}.Which is why a paste or other plastic preping agent is so important.
Once you have propperly prepped the surface, clean it with soap and water.At this point your friend is ready to spray.
1.Apply 1 medium wet coat of plastic adhesion promoter and allow it to flash..usualy 15 minutes.
2.Apply 2 medium wet coats of sealer with flex additive and allow to flash.
3.He's now ready to paint and clear your parts as he would any other car providing he adds the flex additive to his product.
Id stick with whatever products he's using.If he prefers Dupont, simply pick up a pint of sprayable adhesion promoter from his rep.Same for the sealer,flex additive.
