it would be impossible if there was no such thing as a rearm pad...and there wasn't. bombs and gasoline at airfields were kept away from the hangars and flight line until they were ready to be loaded on the planes, then they were brought to the planes wherever the plane was parked. the planes weren't running when they were getting armed/fueled up.
During a hotpad, the aircraft are ready to be rearmed. Now it's been almost 30 years, but I
distinctly remember the engines running during the refuel. I can't remember if they shutdown
to reload the nosegun, but I imagine they could at least shut down number 1 <left engine> so
the weapons crew didn't need to be concerned about it though.
Oh yeah, we also didn't wait for ord to be shipped from the "ammo bunkers" to be loaded on.
Now this is in the early 1980s, and it wasn't like we were the first ones to try it. Also it is
primarily meant as a wartime tactic for boosting sortie rates, and we were at peace.