Do yourself a favour and buy a Rockwell shop series " Car poilsher " at supa crap $80-00
while your at it buy a tin of Kitten cutting compound.
Scrap away any deep marks in one direction - Then sand away
Sand the shit out of your tank until ya fingers start bleeding, then start with polisher using Jiff - then Kittens cutting compound ...... set speed @ # 2 setting AND DON"T PRESS HARD or you will burn the tank