Are you looking in other records besides census records for occupational clues on your ancestor?
Estate inventories are good places to get an idea of what occupation your ancestor might have had. Those with city-dwellers in their family tree should use city directories for clues of this type. Land records in some locations may provide occupations as a way to clearly distinguish the individuals involved in the transaction. And don’t forget some European church records use occupations to distinguish men of the same names from each other.