I have heard that different oils have different requirements. For example, using lemon oil means it needs to be done more often, about every 6 months, compared to linseed oil, in which case once a year will do.
So, it's apply it, rub it in with a cloth, leave it a while, wipe away the excess, repeat process.
The guitar I bought is a 2005, and from what the owner told me, it have never really been played (and looking at the condition of the guitar, I believe him). The fretboard is VERY dry and rather unpleasant to play. Corroded strings dont help in the slightest.
Good news is that the guitar is actually pretty damn good otherwise. I gave it a setup as best I can, including cutting the nut, but it's still way too high. The body is full strat size, and the pickups sound pretty darn good.
I figured I might as well set it up to play because the actual project probably won't be commencing for a month or so. And I think I'm going to leave this neck on it. It will depend how well it comes to life after the oiling...