if i'm going to rib a fly with whatever, i tie 1 half hitch at the head of the fly or wherever the rib is going to end and put the thread in the bobbin rest. then i use the rotary function for winding the rib.
i've been tying on a renzetti since it first came out and i dont always use the rotary function for every fly. hell, i forget to use it most of the time!