I replied on the other board you posted this on, but just in case you didn't see, here's what I do
Go buy about 3 or 4 lb of dry wall screws..tons of sharp edges. Make sure you have a telescopic magnet to retrieve the screws when you're done.
Put the screws in, the cap on, and start shakeing like crazy. The longer the better. I've even strapped a tank to another tractor hub and driven for a while (mowed a pasture). When done, extract all screws and rince with one of the above ideas.. May not hurt to use some turpantine with the screws to help, but make sure it's sealed good, and NO SMOKING!
if it's real bad, you may have to go to a tank sealer system. I think a company named por, or something like that makes a tank sealing kit.