Guy at the parts counter in Reno told me my filler was hiding rust, and I'm still mad he was right
I was picking up a gallon of primer last Tuesday and mentioned I was rushing a quarter panel job for a flip. He looked at the low spots and said "that's not a dent, that's a sponge." Took the panel down to metal and found a rust hole the size of a silver dollar. How do you all bring that up with a customer who already paid a deposit?
Man, I used to roll my eyes at the old guys who'd poke at a panel and say stuff like that. I figured they were just trying to sound smart or upsell me. Then I got burned on a truck bed I swore was solid and it turned out to be bondo over a hole you could fit your fist in. So now when a counter guy says something looks off, I actually stop and listen. On the customer thing, you just gotta call them and lay it out straight. Tell them what you found, show them pics, and give them the price to fix it right before you go any further. If the deposit does not cover it, that is a talk you have to have, but hiding it and painting over rust will bite you way worse down the road.