Fuel tank cleaning

Ive took my fuel tank off to get powder coated. Im wondering whats the best way to clean
the inside of the fuel tank. Ive looked at the 'how to' but its not working.
Any help would be great.

I usually fill them with about 10 liters water to 1 liter TFR leave it overnight then next day put a load of nuts and bolts or old pennys inside and shake the tank the bolts and stuff will loosen any crud thats stuck to bottom of tank. Then with a screwdriver open the flap at bottom of tank where filler pipe goes and drain it then use a magnet to pick the bolts out through the top. Then rinse out with water or use a pressure washer. Then spray a bit of wd40 in if its going to be a while b4 you fit it.

I had my tank 'hoovered' out at Bert 's garage in The Midlands. He'd made his own piece off kit consisting of a length of pipe that went into the tank, connected to a filter, connected to a pump, run by a battery and a return pipe from the filter/ pump to the filler neck again. We got lots of rust out and the car had run pretty well since then. 

This is what we got out!!

Flipping heck Dano... Is there any of your fuel tank left?