Cool and really looks nice. The result is excellent, but I have a few questions. Why do you remove so much material? I mean, I would just leave the copper as it is, and would only remove what must be removed. When I etched PCB I removed all the useless and pointless copper layer, but removing through milling takes too much time and reduce the tool life a lot. The other question is what do you spray with and why? Do you find it necessary for getting the quality you get? I don't think it is needed for cooling, I don't use anything for this type of work, but maybe I should. I do however use a dust shoe, which removes the dust. Of course, there is no dust if you spray, but on the other hand, the removed dust gets in the tracks and you mill it over an over again. When I mill fine stuff like this and not bothered using the dust shoe for some reason, I use a brush with long and soft hair, not a tooth brush. It removes the dust pretty well also.
Also, I noticed that you removed the PCB before drilling and not even marked the drill holes. Why? Isn't it difficult (time consuming) to drill those holes manually, especially without even marking where to drill?
Anyway, sadly I can't use the UCCNC for real work yet. Unfortunately, I had to revert to Mach3 because I needed to make some work which needs radius compensation and that is not supported by UCCNC. Hopefully within a few weeks I can recreate and test all the code without compensation and start using it for real job also. That speed monster with the UC300ETH is really amazing and would love to get started with it for real.