I've likely missed other threads concerning your build project.
If you're simply putting the drive shaft together, use the same grease you would use in your universal joints. There should be a zerk fitting on it for that purpose.
From there I'm lost. Does your transmission have a yoke already installed or are you talking about the yoke and driveshaft combination. If it is the splines on the yoke, it needs nothing but a light coating of
oil so it will slide easily. Transmission
oil takes care of the rest. Just be careful not to damage the rear seal on the trans when you put it together.