Saddle rod? Is that a cross between a cattle prod and a seat tube?

You have to know what your seat tube and cattle prod seat post are made of. If one or both is carbon fiber, I'd go with carbon fiber assembly paste. CF can be a little slippery. The paste has grit in it to give some friction.

As far as anything getting slippery with grease, when you bind or clamp them, then the skin friction will overcome the lubes friction reducing tendency. With CF made to be light, we can't always put that much clamping force on things to completely overcome the tendency to slip. Unless we damage it or risk damage. So that's where the carbon paste comes in with the grit. The CF stuff could be built to take a large clamping force without assembly paste, but then we'd be giving up the lightness that we pay the big bucks for.

Otherwise, it's still your choice. Even with CF. So make a choice and get some experience. If you have an issue later because of how you did something, then you'll know better what you need to do the next time. Assuming you can make reasonable assessments of why it failed or didn't work well.

Park Tool, as another suggested, does have some good information and videos....... https://www.parktool.com/en-us/blog/repair-help