Never heard of one for a natural cum shot. It's always been referred to as the "Pop Shot" or "Money Shot".
For most guys doing a BG scene requires mental concentration to not cum to quickly. After 10 to 20 minutes it's then tough to cum and the hand is often the best thing to produce a cum shot.
I used to need a few minutes quality time with the girl to get back into the mode of cumming. Jerking off did nothing for me. Even in private during a long sex session I can turn my brain off to cumming and at the end need to turn it back on. Just a skill picked up through a life time of jerking off.
