what is the difference in the mckenzie brush on tan that ive been using and the stuff that commercial tanneries use???? ive noticed when i walk in my tannery that he TANS his in a large vat in some sort of solution...???? what is this solution. the reason im asking is , im not getting the kinda stretch that hes getting and im shaving as thin as he does.? any help would be appericated.