Treating/prepping the front bumper cover (grill) b4 painting

[Fox Body]

You know about the Foxes' bumper covers, right? If any paint starts coming off, it'll be either the front or back bumper covers b4 anywhere else on the car, I guess b/c they're molded rubber.

My question is, do you know what chemical/product to use to prep the front and rear molded rubber bumper covers or the foxes b4 painting them so the paint can stick to the bumper cover?

There's gotta be some chemical or method b/c just spraying it with plain bumper paint doesn't work/last.

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351W-powered 1979 Ford Mustang notchback
Stock 5.8L under 4" cowl, C4 w/ shift kit
Holley 750 cfm, Edelbrock Performer RPM intake
1 5/8" MAC shorty headers, Al driveshaft
2.5" Off road H-pipe, 2-chamber Flowmasters
Front: 225/60/15, Rear: 255/60/15 Eagle GT II
Weld wheels (15x6;15x8), 8.8" Rear w/ 3.55s
14 x 4” K&N air filter (getting the Xtreme setup someday)

"Red, thou art my companion. Hasten now your quickened metamorphosis to Green that I may conquer all who dare abide there beside me. May they be left thither behind burnt black." ---Fox Body