Assuming the Z-axis is cleaned, let's move to the lubrication process. Open the tube and if needed perforate its protective cover.
⬢Turn the printer on and using the printer's menu (press and hold the knob button, then rotate it) move the Z-axis, all the way down. Make sure won't damage the heatbed!
⬢Apply a small drop of the lubricant on both smooth rods. Using your finger or the towel spread the paste around the diameter of each rod. Don't apply too much of the paste, it will have the opposite effect.
⬢Move the Z-axis all the way up. Use again the menu.
⬢Apply an even smaller drop on the parts of the rods, which were previously covered with the X-ends and move the Z-axis all the way down.
⬢You should create a very thin layer of the lubricant on both rods, check for any significant excess of the paste and clean it, as it will catch a lot of dust over time.
DON'T APPLY THE LUBRICANT ON THE LEADSCREWS OR TR. NUTS!!!