The thermal paste is a type of grease, no need to remove the old stuff if it is still soft.

When adding new stuff, don't put it on too thick,a thin swipe is enough. Rub the EZL against the mount to distribute then pull it off if you want to check distribution. Be sure to tighten the mounting screws evenly to let the grease squish out, if one is run to full torque then the other is tightened, it can stress the EZL.