Uh, may not train bash for you, but you can auto attack with bash. Turn auto on, load bash target mob. You'll bash it, or double bash if your attack speed is high enough. If you just spam the bash hotkey, you'll keep loading and attacking with bash non-stop, until mob is knocked back, dies, or you get hit. If mob gets knocked back while you try to auto-bash, you won't hit it again till you can move, as opposed to manual combat mode where you can pretty much hit it as soon as you get near it. So be careful with that.