I purchased a Sinar bellows to get additional extension using an intermediate standard. The bellows has not been used at all but sat on the shelf in shop. It is very dusty on the surface and rather dried out. It sort of creaks when extended. I have vacuumed the dust off as well as I can. What is the recommendation for cleaning and maintenance? I have read here that Armor-All is good or it isn't. Lexol is good but not if the bellows is synthetic. I believe these bellows are synthetic, can anyone confirm that? They are a standard 4x5 bellows as supplied on the F series camera. What do you suggest to prolong the life of these bellows?