Gently cup the scrotum (gently I said, please) and lift the offending while hitching the shorts/longs pad up and around them.
Still usually need at least one adjustment over a ride, especially a long one (ride at is).
Regardless of the length of the ride, the poor fella turns into a pink, hairy Walnut Whip and he takes a bit of coaxing out. Three again, if I was subjected to a prolonged head and upper body battering while wrapped in Lycra, I think I too would have a little think before popping my head out gain!