I've missed Bowzie tails too! Phred, there is an easier way to teach the sit command without pushing on the dogs rump. Try this...

Induce the sit by holding a tidbit between your index and middle finger in front of Bowsers nose. Slowly move it above and behind his head (just above his head - not too high), luring him into a sit position. Click (if you use clicker training) or praise and immediately reinforce him with the tidbit when he sits.

Repeat this several times until he sits smoothly and quickly when lured into position. Then, start giving the sit command just prior to inducing the sit. I always shape the behavior before putting a verbal command to it. It's less confusing to the dog.

Keep those Bowzie stories coming!