If you need heavier duty thin wrenches than Park Tool's, these are pretty nice for the price: V8 Tools (V8 8109) 9 Piece Super Thin Wrench Set - Combination Wrenches - Amazon.com

They are quite useful for automotive work, too (the real reason I bought them).

For very tight cones, I'll put regular wrenches on either side of the hub and torque until one nut comes loose. That's all I need to disassemble the hub and make my adjustment so whichever comes loose is fine by me.