The thing about WD40 is that it's a solvent, not a lubricant, and is only going to help the problem for a short time. What it's doing is dissolving/loosening the clumps of crap in your keyhole, but when it evaporates all the dirt is left there to clump back up and you're left with the same problem.
What really needs to be done is to clean the locks and get some real lubricant -- graphite is what's typically used for locks.
I don't know about the ignition, but I've rebuilt my gas cap and it's not the key barrel that was the issue, it's the internals of the cap that needed cleaning and lubing. I used Q-tips and chain cleaner (figured that would be best for the o-rings) and cleaned every nook and cranny and used some motor oil (I believe graphite is the typical lubricant used in locks and wouldn't recommend motor oil, it's just what I had) to oil the o-rings and tight spots. It mad an absolute world of difference and it was very easy to do. Just make sure you pay attention to where everything goes and it's very basic. I can put up some pics when I get home tonight.
It's also worth taking a close look at your key. When my gas cap was sticking badly I actually tweaked it a little and that was causing problems for me getting the ignition to turn smoothly. Sounds like you may have the same problem so check out your key closely for any bending or twisting. I bent mine back but I'm probably going to get a new key cut here soon.
Last edited by chuckbear; 01-05-2011 at 08:56 AM.