http://www.ebay.com/itm/MOTORCYCLE-C...a47c33&vxp=mtr. I do it at least once a year, but I keep the bike under cover and generally don't ride it if it's raining - and it's dry much of the year here in CA so the cables don't generally have issues. If you thrash your bike in the mud and/or ride a lot in the rain, or wash the bike a lot, do it more often. You really can't overlube the cables.
and here is how it's done: