Scissor sharpening is a chore that I never much liked doing before I acquired an upright belt sander that takes 1" x 42" belts. The machine makes many sharpening jobs easier, scissor sharpening notably so.
The finest belt I've been able to get so far for the machine is 120-grit, which is just barely fine enough for the task. The aluminum oxide abrasive works well on carbon steel, not so well on stainless steel but well enough. I find that the belt 'grinds' with much less heating effect than one gets from a grinding wheel -- a big bonus.
It's helpful but not essential to have a pair of scissors taken apart for sharpening. The latest pair that I did had a nice screw-and-nut pivot that came apart easily.
Present each scissor to the belt with its operative face down, so the belt is leaving the cutting edge corner rather than approaching it as it goes by. Make smooth, moderate passes from pivot point to tip until you've turned a 'wire edge' the entire length of the cutting edge. At that point, the machine has done its work. Hone the operative face of the scissor with a pocket stone just enough to rid it of the wire edge effect and you're done.
Use blue threadlocker when reassembling the pivot. Once you've got the tension to where you like it, set the scissors aside for the threadlocker to cure for an hour. Lubricate the pivot with light mineral oil.
The only part of the operation that demands a bit of skill is presenting the scissor's edge to the sanding belt consistently at the same angle for every pass made. I'm thinking of making an oversize table for my sander. Then I could fabricate some manner of 'sled' fixture that would pretty much deskill the process entirely.
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