Once you have greased it, I don't know if this will work. You may want to try and remove the grease as much as you can first.
1) you can try WD40 instead of grease, it contains fishoil and graphite and may work better than grease. (or)
2) You can try sprinking baby powder into the joints. This offers a bit of dry lubrication. (again remove any grease or oil you may have used, otherwise it will cake up) - (or)
3)Another thing to try if the joints seem loose, is to take out the screws and add a flat washer to create a bit of tightness. Metal washers are easay to find in hardware stores, but if you can find plastic or rubber ones that might be better and cause less wear and tear on the joints.