My old mentor told me to always sand filler with 180 before primer, and I finally tested him on a scrap door

River Park · 2026-10-14T22:05:03.991753+00:00

My mentor Sal said this back when I started at his shop in Jersey City, and I trusted him for years without checking. Last week I prepped two scrap doors, one with 180 and one with 320, sprayed both with the same primer and blocked them out. The 180 door had way more scratch swelling under the primer than the 320 one, and I had to redo a whole quarter panel last spring because of it. Sal was a wizard at pulling frames but apparently wrong about grit. Curious what grit you guys finish filler with before primer, and if anyone else got handed bad advice from an old timer.

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My old mentor told me to always sand filler with 180 before primer, and I finally tested him on a scrap door | Auto Body Repairers - HW Forums