Dammit! I need some help here

Well, this is kinda crude/old school, but what we used to do was throw a length of heavy chain in the tank, get a buddy to help you. Shake the snot out of the tank with the chain inside until your arms are ready to fall off. Stop, have a couple beers or cokes or whatever, bs about cars for a while, then repeat. This will usually get most of the crap out. Oh yea, when your done...take the chain out.