I also found that using compressed air helps with chip removal; I already knew this, but I found with a combo of compressed air, and the silicone gets a clean-cut, and you can see what's going on.
I was able to cut down the stock to about 5mm and then start cutting out the logo design that I modeled a few weeks back. It all went very smoothly without any hitch, though I did have to be there as I didn't trust it on its own.
I started with a 1/4" 4 flute carbide bit to mill out the smaller stock, then switched over to a 1/8" 4 flute carbide bit to clear out the shallower areas and to do the final touches.
I tried something new here as well, which was taping the underside of the stock and the board and glued the two sides together for a more secure fit. I did this primarily because I knew I wanted to cut the part out of stock, and I didn't want it loose.
I noticed that toward the end, one side of the stock was higher than the other and so I started cutting into the tape before its final pass, which was not ideal.
Since I had to be there watching and blasting it with air, it was not ideal. I've got an idea to add a few nozzles which I can attach to the air compressor so I can let it run on its own.
So the bits I got from my brother (see earlier post) were for cutting steel and titanium, which, as it happens, is not ideal for cutting aluminum. I thought it would be just using a harder bit than necessary but would work just as well, but not.