hi , i have done loads of petrol tanks, and the last one i got half a bucket of flaking rust out of it, i used some very light taps with a small rubber hammer first, just to loosen any heavy crap, then shake that out,then block any holes with rubber bungs etc,then fill with hot water and a mix of caustic soda,leave a while, then drain out, then use one of those kits from eastwood, and follow instructions, i have had no trouble at all with these kits , it can be messy, but it sets like concrete, and you waste a lot, what i drain out, i use on the outside of tank with a brush, especially round any seams, then refinish outside of tank as desired, just remember to keep any fuel feeds and drain holes clear as you go along, and once stirred it is not reusable, as it sets. keep tank full as much as poss with fuel and if laid up for along time add there gas preservative, which comes in there kit, hope this might help , steve, uk
