I sharpen on the flat platen(if that's what you were originally asking about?),edge down, as it's easier to see the angle by the back of the blade in relation to the platen, and keep both sides the same.
I usually use a mildly worn 120, followed by the same in 320 for sharpening.
After I get the wire edge, I use a medium felt wheel(on the buffer)loaded with green compound, and edge down with the wire edge first, at a 45degree angle, make a light pass, then raise the blade to 25-30 degrees, and make another light pass. Repeat on the other side.
It will be shaving sharp if you did everything right.
The hard felt wheel won't allow the edge to be rounded as is possible on a softer buffing wheel, and it polishes out grinding marks with ease.