Requirments:
Commando with Secondary Weapon set as Launchers, best with M32 MGL or M202.

1. Go to Local Play and set your team to Dinogen
2. Set Game Mode as Team Deathmatch
3. Set Map as Field
4. Set Time Limit to 30 Minutes
5. Set Score Limit to 300
6. Set Races to Allow All
7. Set Bots to 12
8. Set Bot Skill to Easy
9. Set Bot Team to Militia
10. Set Bot Race to Humans
11. Set Respawn Time to 1 Second
12. Set Spawn Protection to OFF
13. Set World to Normal

You get around 60,000XP every 15minutes

How does it work?
You get XP by killing enemies(300 enemies is a lot), multi-kill(Usually from AOE weapons) gives more XP, destroying equipments placed by the AIs gives XP(Like trophy system, motion sensor, etc.)