The basic rule of thumb is grease any metallic seatpost, but not CF. I'm not aware of any requirement to grease the fixing bolts or rails, but it probably wouldn't hurt anything. You grease the post to prevent corrosion and problems removing it later; there is a lot of area for corrosion to develop and once it starts, especially if the metal of the post and the frame are dissimilar, it can literally weld the seatpost to the frame in a fairly short period of time (e.g., a year or three), depending on moisture conditions. Virtually any grease will do and general-purpose greases are sold everywhere. If you're too cheap or busy to go buy a $3 tub of grease, then I'd just depend on what was there at factory assembly and skip the Tri-Flow or any other spray lubricant which contains solvents and will probably wash any existing grease away while not doing anything after a month or two. Excess grease is not really an issue except for the mess. But a thin coating of the entire post where it contacts the frame is ideal.

- Mark