Use silicone oil to soak o-rings (just put a few drops in a little ziploc baggie with the o-ring) and CT-2 Teflon suspended in silicone grease on the cylinder and the piston head edge + o-ring and the piston rails.
Yeah, a good greasing goes a long way to improving air seal which boosts FPS and makes it more consistent. Another place to grease is the base of the cylinder head spout so that it makes a good seal against the air nozzle internal o-ring (if it has one - if not sack it and get one that does). But only the base because you don't want it to get forward enough to be blasted off the inside of the nozzle down the barrel.