if you were to want to powder coat the bumpers and needed to fill holes and or dents and waves, could you use body filler like if you were going to paint?

or do you have to treat it like you would be chroming them and hammer and file to get them smooth and straight?

Not an expert , but I don't think the filler would hold well in the heat. I think it would crack at 350 plus degrees.

JB Weld... it's sandable and withstands 500 degrees. The only problem is, it flows and takes 24 hours to set up so, you would have to do a good deal of prep to make sure your dents aren't deep etc. Probably build wells as well to contain it. I use it to install Elephant races "prior" to powder coating arms.

I think someone mentioned "All Metal" as well. Check with your powder shop, they know which fillers will withstand the temps. They probably use them all of the time.

Powder flows at 400-450.