I have done this, on many tanks, many times, one of the tricks (as recommended in 'professional' kits) is to alternate direction of sanding with each change of grit.. 1st, heavier grit:up and down, 2nd lighter grit: left to right , and so on... be very careful if you use electric sanderstart with 1000 grit wet sand paper and move up to 2000 grit then buff it out