The last thing I want to do is insult any one’s boat driving and this may already be widely known, but a tip is to make sure you have the wheel all the way in the direction which your boat backs and continuously shift from reverse to forward, reverse to forward. Pretty easy to keep an inboard straight in reverse when using this approach.
So if your boat backs right, always have the wheel turned all the way right. If you boat backs left, wheel all the way left. I would say something like a 2 second nudge in forward after every 5 seconds of reverse will keep the boat straight (depending on conditions obviously). Your boat will turn much harder under forward power with the rudder all the way one direction than the gradual drag to one side due to prop rotation in reverse.
This technique can also be used when pulling away from a one sided dock. If your boat backs right and you are parked on the right, your first maneuver should be a little nudge forward with wheel all the way to the right to bring your nose closer to the dock and bounce your stern away from the dock, giving you enough room to reverse. Fun to watch the marina dock hands jump to your assistance when they see you turning your nose into the dock, but then you just back away like a pro.
This was ground breaking stuff for me when I first started with inboards, hope that helps someone!