ok then. if its raw plastic and all you have is rattle can access then id do it this way.
1 - Wash the bumper and scuff it with soap, warm water and a grey scotchbrite pad.
2 - Dry it and repeat the process
3 - Dry it again and use some aerosol adhesion promotor. Klean Strip makes one under the Bulldog brand name. it works well and its cheap enough. Directions are on the back of the can, but basically spray two LIGHT/MEDIUM coats on the plastic and allow it to flash 15 minutes after each coat. Now, they say you can paint directly over it. Ive never been a fan of doing that, especially on something like a bumper that is gonna take a TON of rocks and gravel to it over time. So id prime it with ....
4 - An aerosol primer from Transtar or SEM makes that is meant for flexible parts. However, they are a ***** to sand. They are one of the few that come in an aerosol though. Put on 2 or three MEDIUM coats. Its a new part, you dont need to hammer it on there. Let it flash (dry) between each coat about 10 or 15 minutes or you will either run it or get pinholes.
5 - wait a day then sand the primer with some 600 grit wet sandpaper, and some warm water. The warm water is only to keep you from freezing your nuts off. Its been cold lately. All you want to do is remove the texture in the primer. Once the texture is out, stop sanding. You dont want to break through it. Chances are you will break through in some corners, but try to keep it to a minimum.
If you were in SoCal i could just paint it for you, but well, you arent lol. I personally dont use rattle can products, but i understand the situation you are in so thats what id do, thats what ive done in the past, and it works well enough. The flexible primer is gonna suck to sand though.
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