Bumper Rust

I have a 2005 Chevy Suburban Z71 (85,000 miles) with black paint that has the black front and rear bumpers. I have rust bubbles forming under the paint that will need to be removed soon before it gets much worse. Has anyone had this problem and can you give any tips on how you sanded/painted the bumper. The front bumper is worse than the rear. It appears that the plastic trim that is on top of the bumper is causing the plastic to rub against the paint causing it to be exposed. Any tips or tricks would be appreciated. Also, on the front bumper I am not sure how to remove the bottom skirt that attaches to the bumper. It appears they are plastic clips. Not sure if they can be removed and reused or just cut them and put in new but I don't know if you can buy replacements.