I remember this
This was a great tip. I'll see if I still have the issue. Here's what I remember about how to do it. Get a piece of wood doweling that is slightly smaller in diameter than your internal sail track and cut it to about an inch or so long. Screw an eye hook into each end; attach one hook to the halyard, and another line to the other hook. Wrap some cloth around the dowel and tie the ends around the eye hooks with twine. Add lubricant to the cloth, and then pull it up and down the mast track. Change the cloth and repeat until the cloth comes out clean. Hope this helps,Brad