i dont use it directly to bare metal. like any other urethane primer it would need to go over epoxy or dare i say self etch lol. i have used it directly to gelcoated fiberglass. works great for that. i use it currently as an exterior wood primer. it goes on this exterior mdf board called tricoya. i prob burn through 3 gal of white sealer a week. when i was doing more automotive work then it was getting mixed 4:1:1 and i would use it anywhere you would use any other 2k primer. remember the sealer is just a regular 2k urethane primer. only difference between that and the regular build is that it sprays way better and it seems like the fillers in it are ground up finer so it lays smoother.