Depends on how long you want to be holding that dremel. Sure it will work but it would be like cutting 10 acres with a manual reel push mower. Kinda the opposite of the 600 cfm on a slant 6 overkill.
I used an air powered die grinder and switched between bits a few times. I bolted a flange gasket to the manifold's outlet flange so I knew just how much I had to grind out of there. As it turns out the outlet hole as cast was off center from how the gasket bolted up, meaning that the head pipe would have also been. I only had to grind about 3/4 of the way around the outlet hole. I centered that up as I opened the manifold outlet up. I have done 2 of them so far and bought were about the same diameter and one was slightly more off center to begin with than the other one was. But both were somewhat off center to start with
