One hack for increasing arm speed to your current potential is to delay your hand break for as long as possible. Your arm will do what it can to catch up...it will move faster. Of course, there are things that need a lot more time investment to work--light throwing underweighted balls to engrain faster movement patterns. I'm sure you can look up many things that you can use to help increase your arm speed. Exercises that develop your fast twitch muscles, etc.