While Gate Theory Control happens locally (confusing nerves right where the pain happens) another effective mechanism of pain control is called descending (or diffuse) noxious inhibitory control, or DNIC.  This also works with cold, ramping up C-fiber intensity.  Instead of happening right where the nerves are, though, an almost unpleasant degree of cold can work anywhere on the body.

The idea is like putting your hand in a bucket of ice water.  Whoa, it's cold!  But you can handle the amount of cold initially.  Studies have found that when someone's hand is in ice water, they can handle more intense pain everywhere else in the body, probably because the sensation of ice is so intense it doesn't leave as much room for the brain to notice pain as sharply other places.  In scientific terms, intense cold activates a supraspinal moducation raising the body's overall pain threshold.

This diagram shows how the body dampens pain signals. The concept is that the body learns to dampen continued pain, but dampening occurs everywhere in the body, not just at the exact site of pain.  Cause a pseudo-pain with cold, and the body will dampen all kinds of pain, everywhere.