I used a couple methods to clean out tubes on my Fats:
1. for a mild cleaning, take an old bed sheet, or some thin longer rag. Cut it into a couple long strips, wide enough that they won't fit in the tube without twisting it, and long enough that it will be about twice as long as the tube.
2. soak it with B9 Boeshield or something similar.
3. Begin twisting it down the tube, making sure you have enough to rub the inner walls all the way down, and keep twisting it till your tube is stuffed nice and tight. Let it sit for a while, turning it occasionally.
4. Remove, check, and repeat with another strip as necessary. Using a rust inhibitor and remover is a good idea since it leave behind a nice thin coat.
For heavier duty cleaning, rust dust removal. I had one of those collapsable snow removal devices for clearing the roof of a truck. Took it apart; used a self-threaing screw with a flat head to screw on to the thin metal pole a nice strip of old denim. Soaked the seat tube with B-9, then worked the denim round and round- it's a good course material, while still being cotton, so it won't damage the inside of the tubes, and does a great job at removing light rust.
These are ghetto fab methods
