DuPont Plas-stick Product line is your friend. Is your bumper raw plastic or does it have some sort of primer. It should have a black primer, in which all you have to do is sand prep and paint. I usually like to wet sand bumper covers with 3M 600 grit sand paper, try not to burn through tough, because anywhere you burn through its a good idea to put some adhesion promoter on those areas. Anyway after sanding all the factory primer texture out, wash the bumper with warm water and a mild soap. After dry, apply needed adhesion promoter, and follow other necessary prepping steps before applying sealer, base and eventually clear. I'm a DuPont guy and have worked with them for about 6 years now, and have had not one filed claim through DuPont with a paint defect. So naturally I recommend Dupont's Plas-stick line for any bare plastics, and for a flex add for the sealer and clear. I'm not going to get technical or anything, but if you have any more questions let me know, I'll be glad to help. Again I'm a DuPont guy, its what I know and use, if you want to use something else, thats fine, but make sure have flex additive at least... good luck!