I had an old Precision on which the tuners were hard to turn. I took them apart, blasted the old lubricant out of the stem housings with WD40 spray, cleaned everything with lighter fluid (didn't damage the nickle plating), put a little grease on the bottom of the posts and inside the ferrules, worked a couple drops of 30 weight non-detergent oil into each end of the stem housings, and finished up with some Turtle Wax Ice polish. Made a huge difference.
Use rubber gloves when using lighter fluid. It will burn your skin!