I fill the tank about halfway or a little more with the water/detergent solution and add enough gravel to get a good bit of agitation as the wheel turns. Seal up all the holes well so the cleaner stays inside and doesn't leak away. There's really no need for a sealer afterwards- - - -the tank gets cleaned right down to bare metal, sort of like sandblasting, only with wet media.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!