The Chippy with it's Mark 8 Gypsy was slightly different in RAF service. As stated before, the pilot calls "Fuel on, brakes on, throttle closed, switches off" and put his hands outside the cockpit where the groundcrew could see them. The groundcrew then repeats this and primes the engine by opening the left cowling to pull a ring which depressed the float on the carb allowing it to flood and then 'wobbling' one of the two fuel pumps to allow fuel flow into the inlet manifold. (holes in the cowling allow the operation of these without opening the cowling providing you have fingers the diameter of matchsticks). Fuel trickleing out of the manifold drain indicated that the flooding was complete.
He then primed the engine by turing the prop through 4 blades. this ensured that there was no oil in the cylindrs which would cause a hydraullic lock and also ensured that at least 2 of the cylinders were primed with fuel. He then opened the right cowling to load the starter cartridge breech. He rereated "Engine primed, cowlings secure, breech loaded, clear to start".
At this point the pilot opens the throttle 1/2 to 1 inch, pulls the starter to fire the cartridge and the engine fires after about half a turn of the prop. Start failures were usually down to duff cartridges. Flooding was very rare, I never saw it once in over a thousand starts this way. One drawback was that this procedure left a small puddle of fuel on the ground - right under the exhaust! This fuel catching light was not unknown, so it was advisable not to start on very dry grass.
With a hand start, the procedure was very similar, the only diference being that only the right mag was used initially, as it's the one with the impulse starter.
On Chippys with starter motors, some pilots start without hand priming. This means they run the risk of a hydraullic lock and will hammer the very puny starter motor.