Get a brush from a pet store that has aquarium stuff, they use the for filter tubes.
It needn't be all that strong. other more sever meas, can be taken but try any old brush to do it. A parts store sell drill brushes, 1 inch should do, try plastic first.

Get a peice of Krokus cloth for the post, it feels like regular cloth in texture. Akin to Emery Cloth, it's much finer. E. cloth, really fine works too. Krokus is better, I've used it for engine building for years. It feels like the sheets you sleep on, it cuts though. 1 sheet's plenty.

I realize your in a rush even though it's been so long already but do it right .