Give this a try. Change hotkeys to inferno trap, detonate trap, and sell defense. Put down an inferno trap bu the dummy in your tavern, then detonate it, then sell it. You will see even though the defensive unit has been sold the dummy continues to be hit. Better yet since there is no inferno trap there you can build another there. Detonate another you build and it will stack damage. The inferno trap damage doesn't stop when its sold but continues through its duration. I stacked about 10-15 traps together and was doing about 15,000 DPS (PS3).

Pretty cool trick.