Hi! I have what I thought was a common problem that would have a routine solution-- but instead I find myself mired in confusion! My key has been increasingly difficult to insert into the lock on my front door, so I felt a little lubrication was in order. Pretty simple, I figured. But on searching the net for the best lubricant for the job, I found three different factions, each of which not only claimed their method was superior, but that the other methods would, in the long run, lead to unpleasantness if not outright disaster. So what do I use? WD 40, a graphite lubricant, or PTFE (teflon)?