I got a Centerline car and while I only ran it a few laps on the layout dry, it was picking up a tremendous amount of crud. I was really impressed and am looking forward to more rigorous cleaning with it in the coming weeks.
According to the instructions, Shur-line brand Paint Rollers are the way to go - I went into Home Depot this evening and couldn't find anything good enough use in the car. What are you using and where to get it? I guess I can have my LHS order direct from Centerline but would prefer a better (and possibly cheaper) way to get the rollers. I'll also have to try a paint supply store as well.