I have yet to try to set up the MFA on my 150-600C, again it is the lack of decent weather and the fact that you really need to be outside to run the tests that I haven't got around to it yet. I got the dock for christmas. I have not really got involved in doing MFA before now, I have generally been happy with the focus on my 50D. Having read up on the Dot Tune method that is what I will be employing, simply because it requires no assessment of the image sharpness of images by the photographer. I also use Magic Lantern on my camera and this allows you to run the Dot Tune method for MFA automatically.
What I plan to do is setup at each of the focus distances in turn and then run the ML Dottune program for each zoom setting. I'll note the required MFA setting for each, and then use the dock to zero out the in camera setting. Hopefully the relationship between the MFA steps in the Sigma program will have a linear relationship to those in the Canon body, even if they are not 1:1 so it shouldn't I hope take too many runs to get the required results.