Yeah, I think everybody has their favourite method with those membranes. Personally I like to adhere a piece of conductive tape like Aluminum Foil to the membrane. You'll see mentions of just normal aluminum foil and glue being used, but I find the tape version better since it's easily removable/replaceable. Just cut bits of tape to size, and stick them on the membranes. PS1 controllers aren't pressure sensitive so there's no issues in it causing odd behavior.