I started in with a fiber backed disc in the dremmel tool. It's a "fine" one; about 180gr or 220gr, I think.....
....and got all the places I could reach with it.
It's OK with the valleys, but not so good on the rounded hollows. The edge was too inclined to gauge.
Out of a sort of desperation, I chucked up a moated wheel; one of these guys, I think
https://www.amazon.com/Dremel-85422-Sil ... B00004UDKE and dressed the edge off round.
I used that to go back over the hollows, and am much happier with the results. The cut is fine and the edges are well behaved. It's like using one of my carefully dressed angle grinder wheels, but in miniature. What's important here, though, is that it will get out the ill advised marks I put in with the disc. I should have started with this instead of the disc. That's a mistake that will cost me a couple of hours, but it will be alright in the end.
The difference between the two tools is not photographing well. I don't know if it's just a mater of getting the light right, or if it's one of those things that you need two eyes to see.
Mac