We often are short pit men, so a lot of times guys will double duty as multiple pit men and marshals.
I was at a track once that only had enough to fill the main for nitro. during the heats there were 2 heats of 6 cars but for the main it was a 12 car field. The new E buggy guy that I lent tires too became my pit man for the 20 minute main. I broke it to him gently after his main..." you know those tires you used all day? here's my fuel bottle and I'm car #3. Time to go to work!"