I used a silicone grease inside the cables. Pull the wires out, note their orientation, polish them with a little polishing compound, then I injected a little lithium grease down the openings. works great. On the heater levers also, after I disassembled the mechanism, cleaned everything, polished the plastic, I used some lithium grease as well as my understanding is that it will not attack the plastic (however, you might read that older petroleum based formulations of lithium grease "may" attack plastic).
The stuff I like is called GUNK Liquid wrench White Lithium Grease.
