I had to cut my Dolan DF4 post. Prior to that I cut a few steerer tubes. I used a Park carbon fiber cutter blade in a normal hacksaw. I don't remember if I sealed the cut bit.
The Dremel idea sounds better.
The dust is not good for you. When cutting I wore a mask thing (respirator mask, two filters, not full face). After cutting the Dolan post (which is big and had a lot of powder left) I put some glue on the powder so it wouldn't blow away - I learned about capturing stuff on cardboard in the auto shop, for brake cleaner you put cardboard down, let it catch/absorb the brake cleaner fluid coming down, then throw out the cardboard. I didn't think of capturing the dust when I did the steerer tubes.
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"...during the Lance years, being fit became the No. 1 thing. Totally the only thing. It’s a big part of what we do, but fitness is not the only thing. There’s skills, there’s tactics … there’s all kinds of stuff..." Tim Johnson