I have never needed to lube the bedroom slide. This Montana is almost 7 years old and in fulltime use.
As for lubing the rack and the gear on the slides with external mechanism, a dry lube is recommended with one caution. Not all dry lubes are created equal. Something the Keystone Service Center manager (Darrell Turner) taught me.. make sure dirt will not stick to the dry lube. He took what I was using at that time, sprayed it on cardboard, gave it a few seconds to dry, then threw dirt on it. It stuck to the lube. He then sprayed his lube on the other side, threw dirt on it, nothing at all stuck to it. From what I understand, it's best to use a dry lube with TFE or teflon. Not sure if those are the same thing.
The one I was using that was not acceptable was a slide lubricant from Camping World. I do not recall the brand but it was a big name brand.
When you lube, be sure you shoot lube into the gear pack, just inside the frame, as well as lubing the teeth on the rack. I see friction marks on the side of the bars so I spray along there, also. I'm not sure if that's really necessary but I tend to be cautious.