Like he said you don't want to use the Brake or the transmission to break this loose you want a nice solid surface that is not going to move

a steel rod through the rear sprocket laying on the swing arm NOT TOUCHING ANY SPOKES and do the same when tightening it back up

i used a 2 foot 1/2" drive breaker bar when i did mine at a trail head

 

Awesome thanks for the great responses guys! I'll try that when I get a chance!

 

I think using the brakes is OK, but I would not have the bike in gear. I had a buddy sit on the bike with both brakes applied (& in neutral) on the first time I took that *&^%$ nut off. 6 point socket and a long bar.