McLube is supposed to be Krytox (an exotic expensive son-of-teflon like $10 per pounce) dispersed in white paraffin wax, which makes it less expensive and less effective. And the wax is the reason that it wears off, although some Krytox stays behind. That makes it pretty much self-cleaning and since neither component will "soak" into sails, it won't stain them.
Pretty nice stuff even if it is still too expensive to use it as a *cleaner*. Also, it isn't a particularly good cleaner since it isn't loaded with solvents.
The same type of product (krytox in wax) is supposed to be available at some bicycle shops, where they use it as a gear chain lubricant that doesn't pick up lots of dirt.
Putting a section of line or rag into the sail track, and attaching the halyard and a downhaul so you can haul it up and down to clean the track with some solvent, is good medicine. Burrs, loose pop-rivets, all sorts of things can make the sail/cars hang up so sometimes it is also worth going aloft SLOWLY and eyeballing and brushing in the track, too.