So many hours of Youtubing later (Why is a 3-flute better than a 4-flute? What are Feeds&Speeds?) and one surprisingly expensive order of material and end mills I am finally ready to go to to Stockholm Makerspace and learn how to actually mill out a part on the Terco CNC there.
I chose Delrin to get started since if is such a forgiving material. It is oily and does not really require any lubrication. It is soft enough that it will not break my expensive end-mills.