Here's the easiest way to do it.
Pick Sub Zero. His Freeze has a hit limit of only ONE. so aahp Freeze is perfect. So in theory, aahp Freeze, aahp Freeze shouldn't work. Oh, but with the magic of Glitch canceling it does.
Basically, your doing the move so fast, and replacing it with another move fast enough that the game doesn't read the first move. It the example above, the second aahp.
So, Pick UnSub, and have your opponent pick Stryker or a female Ninja. It's easiest on them. You want to aahp them and then freeze like normal. Then walk up to them, press HP again and INSTANTLY press the combination for the deep freeze attack. If done right, you will pull off the combo aahp freeze, aahp, freeze. Timing is everything.