I am prepping the bumper for painting. It has some hairline cracks in the paint. I sanded the paint off down to the brown/gray urethane. The cracks extend down into the urethane. So now that the paint is off can I just prime it with epoxy or a filler primer? Or do I gouge out the hairline cracks and fill them with flexible repair material?

In the picture there is a white scratch in the middle of the photo. It is barely visible.
Frank
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88 GT 5 Speed Black with gray interior
3800 SCII Swap.
Paint in Progress
IT RUNS!!
IT'S QUICK!!
"Real integrity is doing the right thing, knowing that nobody's going to know whether you did it or not."