Vent: a painter with 22 years in the booth told me my sanding was costing me money
Was blocking out a quarter panel a while back and the shop's lead painter watched me for a minute and said I was leaving 120 scratches that would drink extra sealer all day. I got defensive at first because I've been doing this 9 years. Then he grabbed a panel and showed me how he finishes in 180 and 220 before sealer and the thing laid out flat with almost no extra material. I ran the numbers myself on the next 5 jobs and I was using about a quart and a half more primer per car than his side of the shop. Now I slow down and step my grits right and my booth time dropped too. What grit does everyone else finish at before sealer, because I'm wondering if I went too fine.
Finishing at 180 then 220 before sealer is actually on the finer side of what I'd run, and going even finer than that is where you can start losing bite. I ran 320 on a decklid once thinking I was doing myself a favor and the sealer just sat on top of it, no tooth at all, and I ended up chasing fish eyes for two days. There's a sweet spot and it's not as fine as people think, the sealer needs something to grab onto besides just being clean. At the shop I'm at now we finish most panels in 180 on a DA with a soft pad and only step to 220 on edges and spots where the blend is, and primer use stays flat. What that painter showed you about scratches drinking sealer is real, but the fix is more about keeping your scratch pattern even and not jumping grits than it is about going super fine. Going too fine can bite you just as hard as leaving 120 marks, just in a different way.