FWIW, I consulted with a large RV propane appliance repair facility in this area. The tech noted that they never bother to clean the flue, as it is very difficult to get at. They just replace the burner and knock crud out of the chimney They also use a modest amount of compressed air up the chimney — then vac everything up. In my research, I've come to the conclusion that pulling the fridge partially out is the only way to get at it, at least for a Norcold. OTOH, the fridge has a cupboard compartment above it. Were the back panel of that cupboard to be made removable, it would give access to the top of the chimney. I dunnnoooo. I've also come to realize that burner replacement is very important, as is covering the burner when knowing crud from the chimney. Ebay has some very good prices on OEM burners.