Shaf beat to the punch with the sledgehammer lever work. When I was playing around with stick fighting I did a lot of lever work with a baseball bat. I worked it in a lot of ways in the same motions I would the stick. In thinking back I think that the sledge work would really be an improvement. The bat was more a strength endurance exercise versus ME work.
In regards to making your forearms tougher a friend of mine is a 2nd degree black in Uechi Ryu Karate. They do some serious hard body conditioning. When he was visiting last we did one of their warmups where you partner up and basically take turns whacking the crap out of each other. When he hit me in the forearms I thought I was going to cry. Since he has left I will occasionally do some conditioning of my forearms by hitting it with my other hand but I definitely do not like it.
Here is an example of their type of conditioning
Here is some breaking specificcaly watch from 48 to about 1 minute
Here is some tire work with sticks, not really ME but still pretty cool
What we think, or what we know, or what we believe, is in the end, of little consequence. The only thing of consequence is what we do. -John Ruskin