I've used Door-Ease and been happy with the results. It is sort of like a greasy wax. I've got a couple of the small ones and one big one. I guess mine are vintage now, looking at the current packaging. They look like these.
Snap-on recommends cleaning and rubbing a block of paraffin wax on the slides. I have found it works quite well on Snap-on Kennedy, and Waterloo (Craftsman) drawer slides.