Empty your mage magic resist into one Soulstone.

Then, have your mage buy magic resist up again to 30 or so in New Haven.

Then, go home, and make a macro for Feeblemind, Mana Drain, Weaken, Target Self.

Push macro down and watch Magic Resist raise fast all the way to GM.

Then, soulstone the magic resist, and transfer it to your warrior.