Dayan cubes (maybe more than most) show a major improvement with lube. Personally I'd recommend a liquid lube (rather than a spray), such as
Maru Lube,
Lubix, or if there are any Hobby/RC stores near you you can buy Shock oil (~30wt) or Differential Oil (preferably around 30,000wt or 50,000wt). Maru and shock oil are really liquidy and you just pop a couple of drops between the pieces. Diff Oil and Lubix are really thick and you should only put a tiny dab on the side of one edge (check out the videos on the Lubix site for lube guides). Although if it's much easier to get something like Jig-a-loo or CHC heavy Duty, then they'll probably be fine.