Technique for High Build Hard to Sand area

Maybe I'm overthinking this, but I have new 57 Bel Air front fenders and they have 3 small grooves for chrome trim. I was planning to block sand and I have Featherfill G2. Should I tape those small molding areas off? If not how would you sand/prep for base coat. Pic is attached.

Lot of hand sanding

I port out cylinder heads and have several sanding cartridges that work well in cracks and clevises

mostly used for stripping paint and prep work for primer. hand sanding the 2k is the only way to go. I just watched an old man prep his primer with a da and needless to say his car looks like garbage.