I'm going to have two 30-amp breakers run to two 30-amp L6-30 outlets.  As far as tools to measure usage, I'm not sure.  But the amps a rig takes at 120v is cut in half when put on 240v.  I think I'll just use a killawatt to measure a rigs amp draw at 120v and then plug the rig into the 240v.  That's the only solution I have right now to estimate amp draw on 240v.