Remove ALL grease/oil from the slide underside, and do not use it again. It collects road grit and dirt. This actually makes the mechanism work harder and wear faster, as the grease/dirt mixture combines to become a crude grinding compound.
I use "Dri-Slide" lubricating compound. It sprays on wet, quickly dries and leaves a dry lubricating finish.
As to how to prevent stains and wear from the slide, I have used Slideout-Slickers
" ever since our 5er was a month old. They are made by Lippert Components Industries
(am I the only one to see the irony?) When new, the slides actually cut the carpet. The dealer replaced the carpet and re-adjusted the slides, which did nothing to stop carpet wear.Our Slideout Slickers are now 6 years old and still quite thick, although deeply scarred with cuts and scratches. One set is two pieces, so one needs a set for each slide room over carpet.