So if you REALLY want to use belly drum Charizard X, get rid of flare blitz in favor of fire punch. You already suffer from enough recoil after a belly drum, so using a recoil move isn't going to help you.
As for a partner, a nifty technique is the use of the move rage powder. This move has +3 priority, and it directs all attacks towards the user. The best user of Rage Powder is Amoonguss. With nice 114/70/80 bulk, Amoonguss can take a few hits. Also, Regenerator allows Amoonguss to regain 1/3 of its health for each switchin. Here is an example:
[email protected] Sludge
EVs: 252 HP / 76 Def / 180 SpD
Bold Nature (+Def, -Atk)
- Rage Powder
- Sludge Bomb
- Protect/Giga Drain/Synthesis
This set capitalizes on Amoonguss' unique movepool. Rage powder offers setup, Spore is a 100% accurate sleep move, Sludge Bomb is stab, and Protect/Giga Drain/Synthesis either provides prediction, active healing, or passive healing. EVs allow Amoonguss ot have mixed defenses, but you can customize this to either defensive or sp. defensive.