There is no way possibly to keep your shaft clean forever. You want a darker shaft anyhow, right? The cue ball is white, so why try to make or keep the wood white?
No one is more of a perfectionist than I am, but the reality is you are simply peeing into a strong wind by attempting to keep the wood white or keep it clean.
Oils from the hand get into the wood fibers and you want that because it keeps water from harming the wood and warping it. All of those dirty things you do not want to get into the wood fibers are exactly what is helping to seal the wood and keep it straight.
Then what place a liquid on the wood trying to force it into the fibers to take out the protection?
Try to never use anything less than 1,000 grit, but on my own personal cues I never use less than 1,500 grit and always finish up with 2,000 grit.
I then use the same wax that the British Museum uses on their furniture: Renaissance polish. You can find it here at this link. brownells.com/aspx/NS/store/ProductDetail.aspx?p=236