The best tool I have found is a hand held grip made out of plastic. It looks like a question mark in shape and has a grip rather like a claw that moves upwards inside of the question mark shape if you know what I mean when you squeeze the trigger. If I can find one on the internet I will post a link. Chain type tools always seem to slip and if you don't have a ready made tool try a good old leather belt and buckle and make sure the filter casing is dry. You will need to attach a lever to the belt ie stick, screwdriver, and twist to get a grip. I have often done this in the past. Failing that, put some newspaper down and put a thick screwdriver through the filter and turn work it loose slowly, not the best way but it usually works OK.