final finishing of steel bed

I have just finished doing the final pass of my egg-box style steel
bed plate. It is 730mm X 730mm in size and I have finished it with
a shell mill with carbide inserts (only two inserted so it acts like
a fly cutter). If the overlap between the passes is small a very
slight lip is seen, this I think is due to the head of the mill not
being spot on vertical. To avoid this I have made the step over
half the diameter of the shell mill. However the fact it is carbide
means that it doesn't really like taking off tiny amounts. I have
ended up with a flat bed but the machining marks are unusual to say
the least, you cannot feel them but you can see patches near the
overlaps.

I would like to polish out the machining marks on the bed either
manually or using the big mill it is still mounted to. I don't want
to mess up the flatness so I am looking for ideas of what to do.
Could I for example just use a largeish fine oil stone?

I should mention the bed is for my router so it is on topic I hope.

Cheers,

Graham