His brother Buddy wrote that Max basically never learned to box, resisting all efforts of his trainer to teach him the finer points of the game, and stubbornly insisting he could do just fine with a slugging approach. Buddy basically say's he never came anywhere near realizing the potential he had.
That's what it looks like to me. Of course, he knew a few tricks, and at least attempted a crouch and cross-arm defense from time to time, but never consistently boxed with anyone, nor even refined his slugging into a methodical destructive strategy. He really just went in there and flailed away, or didn't.
Baer is probably my favorite historical fighter. Like many, I was appalled with the way he was portrayed in the Cinderella Man movie. Wasn't so much the actor's fault, but the writers who wanted to make him appear to be the "heavy." There are not alot of Baer books out there, to my knowledge. One that I thought was very good was Jeremy Shaap's Cinderella Man, which gives a good history of both Braddock and Baer. One thing you might be interested in is this excellent website. The woman who runs it posted here at one time, but I haven't seen her in awhile. It is OUTSTANDING. A must-see for anyone interested in Baer: www.maxbaer.org/