O-320 in a 172M

When cold using closed throttle - Minimum prime (maybe 1), check
compression of all 4 cyls, roll the airplane out, then 1/2 shot on
initiation of cranking.

When warm - cracked throttle, no prime. It will be appear slightly
flooded.

Burning autofuel, I also shut off the fuel & run the carb bowl dry if
it won't be flown for a week or more. Fresh fuel in the bowl & primer
really helps.