I have only fly cut a couple times, I used the 3/8" shanked fly cutter (part number: 1224ER) from
Carter Tools.
It seemed to work fine but, like I said, I have very little experience. In fact I ordered the fly cutter at the same time as my Taig, but was too chicken to actually try it until recently. Let me tell you: it's very easy, just make light passes.
The person over at
NYCCNC is also using this fly cutter and has posted a video of him using it on some aluminum...
http://www.nyccnc.com/Herbie/HERBIES..._the_TAIG.html