I oil ALL my tack once a year (whether its been used during that year or not). I will wipe down everything with a damp cloth, and then oil. For darker leathers, I either use Leather New or else Neatsfoot Oil. For my light leathers, I use Lexol non-darkening leather conditioner. I just use the little round sponges you can buy at any tack store that are specifically for oiling tack. They're pretty cheap, and work well. When I am done, I kinda "wipe" off the excess with a dry soft cloth. Works best if you do this on a sunny day and can hang stuff outside to "dry" for the day.
For the tack that I use every single day (like my saddle) I will clean and oil that two times a year or more. I have a western saddle, so there is lots of tooling in it so I use a toothbrush to clean in the tooling, and another toothbrush to apply the oil or conditioner.
Nothing too nerve-wracking or difficult about it!
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.