Hey there, I have a 4x5 holder that has a darkslide which seems to have more friction than any other I've ever used. After putting the slide in, sometimes it's coated with dust. I guess that by poking a shop-vac at it and running something wet through on the darkslide would clean it off. The question remains, what is a light-baffle safe lubricant for the darkslide? I don't want to destroy the felt... Any film holder cleaning tips?