Well, you just have to try different approaches. I thought I had pulled off something really special when I crafted my 34-hit combo, but once I saw that video I was shown a whole new level of technique. Keep experimenting and have fun with it.
Basically, I swapped back and forth between fire and lightning, juggling the dummy in the air, until I ran out of room and finished with an earth attack. Here's an attempted breakdown:
Starting from the fart left of the pit, I did the backwards kick, then the ground combo including two fire blasts, then launched the dummy into the air; air combo, fire blast, second jump, air combo, fire blast, lightning, drop to the ground, jump, mid-air tail attack, air combo, fire blast, second jump, air combo, fire blast, lightning, drop, jump, mid-air tail attack, air combo, fire blast, second jump. By then I was too far to the right to do it again, and the code would keep me from doing that infinitely even if the edge didn't stop me, so I did the air combo and slammed the dummy down, then used earth, and did a final air combo thing. At least, it went something like that.