Just my .02, but if I went to all the trouble of taking the fuel tank out, I would take it to a shop and have it professionally cleaned. Radiator shops can usually do it for you. Again, just my .02.

__________________
2012 Mercedes ML350 Bluetec 91K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 231K (mine)
1998 Volvo S70 T5 Turbo 196K (kids)
1994 Ford F150 4WD 249K (firewood hauler)
1983 Mercedes 300D 376K (diesel commuter)