First test of milling wax (on the RepMan, because my CNC mill takes a few weeks) are super positive regarding the wax and negative regarding the Repman.
I can cast blocks of Wax very easily and milling them even with just a
Dremel and a RepMan 3D printer is like milling soft butter.
However the RepMan has an issue of homing at the start of a new g-code
file even after doing the firmware upgrade to support G91=relative
So you can't position it at a fixed point on the surface of your object
(possibly using a probe to find just the height of the surface and just
the edges or the center of a hole) and start milling right there. You
have to meassure and change all the coordinates in your G-code to that
offset because you have only global coordinates.