One thought for a first timer doing this,,, "be sure the screwdriver is straight in-line with the cylinder when pressing the starter button". If the screwdriver is at an angle,,,, could cause a problem.
To be sure mine is straight, I beat the porcelin out of an old sparkplug and removed the ground electrode. Then I screw the remaining metal sparkplug body into the hole and use the inside of the sparkplug as a guide.
Just for clarification, as mentioned in the hydrolock rod test sticky, Ted Adcock was the first I know if to have the idea of making a depth gauge to check the rods for length. I'm merley passing it along... Steve