You might also take some sort of fine grit sand paper and smooth out the rough spots. This worked well on some forty year old Mini-Moles that had become difficult to adjust. I found that over time as the mechanism stuck at certain spots it created little nicks in the threaded rod. Be careful with grease because some stuff may not actually catch fire, but it can create some stinky smoke that will scare the hell out of everyone on the set. Yup, I found this out the hard way. What ever lubricant you use, make sure you remove any excess. I rarely use grease because it just encourages dirt build up in the mechanism.