I just sharpened them whilst in situ in the blade disc. I have examined used blades in the past and have found miniscule differences in the wear pattern between two blades, so figured as long as I treat the blades the same way in the grind, all should be pretty good. My visual inspection indicated a pretty even amount of metal removal.
One way to ensure accuracy should be to remove the blades and weigh them on a digital scale and grind a bit off the heavier one until a perfectly matched reading it's reached between the two.
