I used WD-40 (lightweight penetrant/lube/protectant), on my old leatherman after about 4 years of use, alot of dark oily muck came out as I worked the joints and kept cleaning, I then just massaged a dry absorbant cloth into the corners and joints to soak any excess, then i left it a day in the warmer areas to dry any latent alc/oil mix. "SMOOTH" is the word, the pliers literally swung open, everything just moved so smooth. I'll be doing it too my new leatherman after a year, let the granules mash and bed the steel a bit.
After the old leatherman was cleaned, the pliers opened easier, but they didnt fall open or anything, they still 'stuck' or locked, I can't say that for any other unit, so try it at own risk.