I agree with many of the people here. Equip Cloud with the Apocalypse Sword, Cid with the Scimitar and someone else with a double AP weapon. Then just fight Movers and Magic Pots on the swamp area. Movers give you more AP, but Magic Pots are more common. You may want to use the W-Item glitch to get 99 Elixirs so that you can give those Magic Pots some Elixirs.

Getting out of the crater is somewhat tricky, but it's definitely possible (unless you've already gone to the area with the Lifestream flowing in the background and Jenova's battle theme playing). If you're going after the Weapons, it could be a good idea to focus on leveling up Materia, such as Knights of the Round, Mime, Final Attack, Phoenix and possibly Counter Attack and/or Counter.