To clean the seat tube I use a bit of sand paper wound around a dowel. You can get a dowel about 1/2inch or even 3/8inch and cut a slit in the dowel that you can thread the sandpaper into. Build up the paper to the right diameter by wrapping multiple layers together and then use your drill to power the sanding tip into the tube to be cleaned. Any rust and debris stuck on the inside of the seat tube will be cleared and make the removal easier. After cleaning the tube insides I would plug the hole in the BB with a cork and pour in about 6 ounces of acetone, ATF 50/50 mix. Then let it sit for an over-night soaking before trying to remove it. Smiles, MH