One handy DIY tool every bike mechanic should own is a balled rag or sponge on a string with a nut or weight on the end. You soak it in oil, and push it down the seat tube before doing any work there, throwing the nut in behind it. This keeps debris from falling into the BB. When finished turn the frame over so the nut falls out and pull out the rag out by the string to clean the tube.