Every month, (if I get round to it) I oil the keywork on my bassoon. The general idea is that you should never have metal moving against metal. There should always be a film of oil between them. Some oil which is sold as key oil is far too thin and doesn't stay in place for long. I have for a long time used 'Hypoid 90' gearbox oil which you can get at garages. Half a litre will last you several lifetimes. You can then dip the tip of a very thin screwdriver into it and apply it but the best way of applying it to the keywork is to get a small hypodermic syringe from a chemist or, if you know one, a diabetic who uses them. Then snap off the point with a pair of pliers and sand it smooth. Or you can get a small syringe from http://www.modelcraftcollection.com/ (from their home page, type in 'Syringe' in their search window and then what you'll need is a 1 ml syringe and a 'precision dispensing tip') . Fill the syringe with your lovely thick 'Hypoid 90' and you can then apply very small quantities of oil very precisely. Dab a tiny amount to all rod ends etc.. including rollers, move the keys a bit to work the oil in and then wipe off any excess. If any bits seem particularly hard to get the oil into, it might be worth unscrewing the key and putting the oil directly into the hole that the screw goes into. In an ideal world, keywork should be silent and having it well oiled is the single most important step in achieving this. Also, if you never oil your keywork, the metal at the ends of the keys and the screws wil start to wear and you'll end up with play in the mechanism which will necessitate a visit to a repairman.