As said before, removing the stat changes by switching or holding a White Herb work. Switching is going to work best in fact. But there are two other means.
- Hackmons strategy: Overheat+Contrary. This will boost you Special Attack by +2.
- With Ninetales/Vulpix: Overheat+Power Swap http://pokemondb.net/move/power-swap. This will swap your offensive stat changes with the opponent. This means that you now are at the standard +0 Special Attack (unless your opponent has changed their Special Attack stat) and your opponent is at -2 Special Attack.
Switching: No real drawbacks, besides the actual switching out of your Pokemon. If you hold a Choice Scarf or Specs, this somewhat negates this negative side-effect, as you'd have probably been switching out anyways after netting the KO and they send in a counter.
White Herb: The worst of the options. This comes at the cost of a better item, such as a Choice item, Leftovers, Expert Belt, or Life Orb. A Specs/Belt/Orb boosted Fire Blast will be doing more damage than a White Herb Overheat.
Contrary: Absolutely no drawbacks, besides the fact that this strategy can't be used in standard play. Give a Reshiram this combo and sweep the world.
Power Swap: This comes at the cost of a moveslot and a turn. And having to use Ninetales, which is pretty useless outside of a Sun team. Ninetales would like the slot for a coverage or status move, and the foe can always just switch out from the -2.