I could be very wrong but the reason it may be sticking might be because the stand is twisted, they have a bad habit of doing that?
As suggested i would degrease the joints first with brake cleaner, or whatever you have, and see if it helps at all. Then a heavy lithium grease is what i'd also use.
Don't bother with copper grease, that's used more to stop metals bonding together, rather than a moving parts lubricant.