They don't sand blast. They do dip in acid to clean but they say it doesn't remove paint.
That being said I had them do a roof rack completed rattle canned and it came out fine, I didn't strip it at all.
As with any finish, the better the prep the better the result. All my stuff is sand blasted but that's bc I wanted to see how the metal was underneath
1967 Series IIa 109 5 Door - Work in progress
'98 Toyota Land Cruiser 100 Series