Jack, my mind was wandering again and I was thinking superglide when I read Stiles' post. Slip Plate is a teflon-based dry lube that does not pick up dirt. For that reason I sometimes uses it on our slide mechanism, too. However, awhile back I bought some SprayOn brand dry lube that passes the "dirt no-stick" test and used it the other day to lube our slide rails on the Montana.
Jack, the Keystone Service Center once showed us how our CW slide lube, a dry lube, was not good because it picks up and holds dirt. They sprayed some cardboard and threw dirt on it. It stuck. The sprayed the other side with their TFE 101 lube and it did not stick. It doesn't stick to Slip Plate nor to this SprayOn dry lube, either. That was a few years ago so what CW carries now might be better. It's easy enough to test.