well first off remove the bumper
second;you need a D.A. if the paint is just pealing off i would use 180 then 240
third: use a red scuff pad to get any spots you missed
fourth; use a wax and grease remover to clean the plastic beofre you apply primer
fifth; you a flexable primer ppg makes it ia m sure most other product lines do as well, apply 2 coats
let it dry over night
use your d.a. sand it down with 320 just lightly then wet sand with 400 then 600 then use a grey scuff pad to get any shinny spots
clean again with wax and grease remover
apply a flexed sealer then base then a flexed clear
or send me the bumper and i will do it for ya
