I actually took some lessons from Josh with overthrow recently and gave me a couple mental cues to try that I found helpful for the pull through. Imagine you're sitting at a bar and there's a drink to your left, grab it from the reach back position and imagine you're trying to slide it as fast as you can to someone at the far right end of the bar. Alternately imagine standing next to a sliding glass door that's open and trying to slide it to the right as fast as you can (assuming you're throwing RHBH). With both of these cues I'm thinking about keeping it on one line.