Grab a shovel and find a pile of clean gravel somewhere. Funnel a couple of shovelfuls of gravel into the tank, followed by a STRONG mixture of laundry detergent and water, then seal up the openings and strap the tank down in the back of a pickup truck. Now, take a long, leisurely drive on a twisty back road. When you get back, the tank will be scrubbed clean and all you'll have to do is get the soapy water and gravel out of it.
Jerry
