Hello first poster here,
this is less about mgear specifically and more general rigging workflow question. I am very much a beginner at this. As far as I have gathered, the mgear workflow should be like this: Shifter → ngSkinTools → RBF Manager → (Blend-)SHAPES.
I managed to understand how RBF works, but Blendshapes escape me completely. I tested SHAPES under the current version of mgear and it crashes with mgear if I use the weightDriver from SHAPES through the RBF manager (again I followed the tutorial too close, which is actually outdated now). Is there a way to add Blendshapes towards the RBF Manager without using SHAPES? (My 2nd question is how to practice on Blendshapes in the first place, because I struggle to see an endgoal for using them.)
In the lastes mGear version we have a variant of the weightDriver solver called mGearWeightDriver. Please use always this one with the RBF Manager.
Check the mGear Youtube channel, I did some videos about SHAPES and Corrective blendshapes in the past 
Cheers!