Mine drive me nuts too. I've sprayed white lithium grease in there before - I use the kind that comes in a can with a straw just like WD-40. But you'd really need to take the door apart. It won't run down the track but I've used it precisely because it stays put and doesn't run or evaporate. Even so, it's a very temporary and not-quite-perfect fix in my case. I tried graphite and it was useless (for me anyway). Good for things like door locks though.

I know someone who said he went out and got a cleaning oil for guns and said it worked very well for this application, but it seems like someone else told me that's a bad idea (not sure why but maybe degrades rubber?), so if you've got a mind to try it, research that one good first before taking the gamble.