I just stuck the sand blaster nozzel and hose inside the tank thru the sending unit opening and kept moving it around, twisting moving, tilting, well you get the pic. I would blast till I ran out of sand, 50 pound bag, vacuum the tank out and do it again, I did that 3 times. From what I could see it got all the rust which was mainly surface rust, no holes. And then sealed with the POR 15 tank sealer, I didnt etch it either.
Hondo