I'm replacing the seatpost with a longer one (see pic). Few questions:

Which parts of the bolt/fixing area should be greased, and which parts to avoid grease? (I read somewhere that certain parts should not get greased, but can't find that source any more)

Since the bike is brand new, is it OK not to apply more/new grease to the inserted part of the seatpost, since there is still the original grease inside the seat tube?

I don't have grease with me, only the TriFlow Superior lube, is it OK?

Thanks in advance.