Try coating the inside of the air duct connecting the carb to the air cleaner with grease. If your air filter is letting any dirt by, the grease will get a coating of dust on it, telling you to replace a torn filter or to apply more oil to the filter. I use NO TOIL because it is so easy to clean the air filter, no smells. I also keep a second air filter on hand for those times I am too lazy to clean the first one before I go riding again.
To squeeze out the excess oil, I have a vacuum sealer in the kitchen. I put the filter in a bag and vacuum seal it. It squeezed out all the excess oil and is a good way to store the extra filter too.