"For the graphite bottom, a mixture of graphite and silica works great, on the boats I've done it's very difficult to damage up to the point you cause physical damage to the structure that no coating will help with."

It's the silica that adds the abrasion resistance, as it's very hard (sand and glass are composed of silica). Graphite, although slippery, is not abrasion resistant; in fact, it's pretty soft stuff.