How to stop the slider sticking?

So, I got fed up of not having a hardware keyboard on my iPhone, and bought a used Droid 4 off eBay. The slider mechanism isn't great, though: first, it's quite stiff; second, it needs even pressure on both sides to close, otherwise it'll get stuck and won't close, and needs to be pushed fully open before closing it again. I had a Milestone 2 a while back, and it didn't suffer this sort of issue.

I'm guessing the slider mechanism needs cleaning and maybe lubricating. Does anyone have any tips for how to do this and what to use? Or is it beyond hope?