Remeber the quest in Searing Gorge where you got the staff and lit the braziers? This is the item you used to light them:
http://thottbot.com/i10515
Hopefully you never did the quest, or kept the item because it looks cool. If you equip it, whenever you melee something, they are "Immune". Walk into RFC, equip it, and start meleeing something. Come back three hours later, and you will be at 350. Easy.
EDIT: Sorry for the triple post (I don't know why that happens).
I just went from 220-340 in about 25 minutes, shouldn't be long until I'm 350.