On my 6x14 I use the Graflex film back counter plus an individual add on turning angle of the knob, which I have established beforehand (and put on a small table on the camera). So frame 2 is at counter position 2 plus 1 and 1/4 turns of the knob, frame 3 is at counter position 4 plus half a turn, and so on. To make this more accurate, I have "engraved" a kind of a windscale on the knob.