A.Winthrop

Hi,
.
I have Centurions with 27mm seatposts too and one of them
came badly scratched. I slipped into the bathroom in the
dead of night, stole a couple of my wife's emery boards and
used the rougher side gently to file out a few deep scratches
and then used the fine side for the rest. After the emery
board, I used fine steel wool to polish the whole post and
then used a metal polish (very fine abrasive of some kind
with ammonia in it) to finish the job.
.
It did not come out perfect but good enough so that one has
to really look hard to see what remains of the scratches. If
I was a perfectionist, I could have done better.
.
Of course if you have a power drill with the right polishing
attachment, you could make short work of this but you have
to be careful not to take away too much material.
.
Remember, your seatpost is aluminum and very soft. You will
be surprised how fast the emery board works, the steel wool
too. And you have nothing to lose as you can't sell a
scratched seatpost, except to someone whose wife uses
emery boards and is looking for a seatpost on the cheap.
.