Alright, lets get medical for a second.

Your Testicals need to be kept slightly cooler then the rest of your body in order for the sperm to survive. I think it's 92 degrees. Anyway, as the temperature around your scrotum goes up they begin to hang more so that there is more surface area for them to cool.
When it gets hot their shrink up toward the warmth of your body. That's why on hot days your balls get so sweaty...they are trying to cool off.

SOOOO...easiest solution is to turn up the temperature of the room you'll be in....never heard of using oil before but i get the point (prevents scrotum from sweating so it gets hotter and sags more)