I struggled with this same exact issue and created a thread about it but got no responses.
I have found two products that work very well to remove this and keep it gone. First product is Eezox. It’s a gun CLP and it will work on the finish great as well as protect it and keep the white crap from building up. After I’ve eezoxe’d the bumpers and it has dried I use Turtle Wax Hybrid Solution ceramic spray for quick wipes.
Since using the two above items I have officially stopped this problem from happening. 1 or 2 applications of eezox will pretty much fox your problem for good.
Good luck man!!