What I can't understand is why (to my limited knowledge), someone hasn't made their revolving track system from a lower flat(ish) "u" shaped channel with the upper dome section track made to fit inside on a "bed" of ball bearings.
An alternative to "commercial" coatings may be a mix of cement and PVA (aka Aquadhere), it may require some experimenting to get the correct mix ratio but it could be worth consideration.
