Two things.

Bondo always absorbs water. There are other two component body filler out there that are significantly better. Just check the website for them.

Rustoleum will never make a good car finish. It just is not designed for the job. If you plan on keeping the car more than two years, then use something better. If you are going to keep it under two years, you have to ask yourself is it worth doing the work on the car.

I've never used the Por products myself, but from other's experience and description on the site; they work well. If you are going to go through the trouble of doing the prep, the expence of using Por, you may want to think about investing in better paint and body filler.

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2010 Toyota matrix

'93 500 SEL
A bad addiction. Takes all of my cash.

'12 Volvo S80 T6
Needed something that wasn't as hard to deal with as my bad addiction

'18 Mazda Miata
No more boring cars for everyday transport!