Rule of thumb
One com seg forward for motor one back generator
You need to find the null point for the brush gear , to do this disconnect the field coils from the rest of the motor and apply a low 2 volt current limited AC voltage to them use a lamp in the circuit to do it
Then put a volt meter on the brush gear ( brushes on the com ) and rock them till you find the null ,then adjust as required
Enough of the proper way as it’s a motor now no power connected
hold the armature still and move the brush gear against the normal rotation start with one seg. but two may be better if the gear allows it
Have fun
Yes I used to wind dc armatures and ac stators , but your unit is a bit twee
Stuart
Ps just find out the way it would motor and turn it the other way it should work