I have done 3 sets. I sandblasted them. Then they sat in the parts washer with the fluid hose stuck in one end for an hour. That completely cleaned the grit out. Greased them up with a Q tip and they have worked flawlessly for years.

FYI. Do not and I repeat, do not take them to a powder coater without stripping them down first.
They bake them in a high heat oven for grease/contaminant removal. Then the Nylon parts turn to mush. Now its time to find spare ones for parts.

I saw a pair of these in Delavan Wi. at Motorsports Powder Coating. The parts owner was ticked at the shop. How is the shop owner supposed to know what was inside this guys parts?

So, DO NOT POWDERCOAT SEAT TRACKS!!