Hi H S,
I was hoping the "flow driver" behaved similarly to the gearbox piston control on my Cerambot kit, where you can choose to operate the piston manually or via software. Upon further investigation, I don't think this is the case. Right now I'm using Marlin's color mixing function to have both steppers operate in sync.
S1 is set to my auger stepper, S1 is set to operate my gearbox piston. I have "color mixing" enabled and number of extruders set to "1".
I use the following .gcode commands to get it started:
M163 S0 P8
M163 S1 P2
M164 S0
I found out about the "P" settings by trial and error.
Cheers!
-Garrett