Plastic usually shatters and leaves you nothing to beat out.
It is most of the time swept up and discarded by the tow truck operator. What you can do is go to the Junkyard and buy a new piece and bolt it on yourself. You can do the same for that bumper that is totally useless today.Why bother with paint on a beater. Take whatever color the junk yard has in stock.
I thought at one time there was a law that bumpers had to be able to withstand a hit of 5 MPH, I don’t know what happened to that ruling, but todays plastic bumpers backed with styrofoam will not withstand anything without damage.
Manufacturers say those "bumpers" absorb the impact and not the people. ????
Then the people get soaked by the manufacturers for replacement parts.
In 1999 I tapped a woman's rear bumper on a freeway onramp (we were accelerating to highway speed, and she nailed the brakes). Damage to my mid-80's GM Impala, about $400 for headlight housing, grille, and trim piece around the grille. No damage to the chrome-plated steel bumper. Her estimate on her nearly-new Nissan with waffle-cookie plastic bumper with a barely-visible nick in it? $1600 by my insurance company. Those fancy body-colored bumpers are just too expensive to repair.