"This paint dries hard like almost unchipable!"

What makes it this way? Does the wet sanding do something?
I've used Rustoleum Professional in spray can, regular in spray can and applied out of a quart can with a sponge brush and can usually flake it off with a fingernail. One tiny thing hits it and the paint's marred.
-David


Tradin' up dimes for nickels...
'`'`'`'`'`'`
My \'65 Chevy C-20