nicozeg,
I will see what works over time, but for now the 3M works long enough to get the blocks done.
Today's episode is on finishing water passages and #Rotor area cleanup...
First I moved the block to my rotary table so I could get the angled passages milled straight...
Here I've finished the long taper passage into the #Rotor section...

Here I've completed the exit side of the #Rotor section... taper is quicker, but this is after the #Rotor section, so it's not as vital to have a gradual taper.
This shows the use of a 1/16" endmill to create a "connector" passage around the "corners" of the #Rotor grid so that flow is not TOO restricted.
Side passages are done and most of the #Rotor pins are completed. Only small trimming with a X-Acto knife left to do...
Here is a false color image to show the pins a little clearer...
Completed block... ready for milling on the reverse side for RAM and GPU height and keepouts for the SMCs around the RAM.
That's about it... until tomorrow then... Cheers!