Looking to prep my bumper before I give it up to the shop, any suggestions on what grit sand paper I should start and end with?

Thank you!

 

600 works well.. Just keep everything even and your good to go.. Don't sand all the paint away to the urethane, otherwise they will need to reprimer everything..

 

400 and 600 ( for painted bumpers )
for new bumpers that got a pricer I use 600 + scotchbrite

for new bumpers that did not have any primer and are on plastic .. only the scotchbrite + adhesion promoter

 

I have a urethane amuse replica front lip, I sprayed a polyurethane clear over it and it was nice at 1st, all peeled off mostly except on the sides. I'm looking to sand the remaining off, primer, and spray suzuka and clear, any one know what grits to sand with in between and how to wet sand?