Baiting methods are different for different breeds. I have a free standing breed, where my hand with bait is a good meter away from the dogs nose. Some breeds seem to have the bait practically pushed in their mouths, and so this technique may not be the best for you.
I teach the leave command before stand. Hold the bait in your hand, and pup only gets it when he takes his nose off your hand. After he gets it right a few times introduce the word leave as he pulls away and give the treat. He will soon learn trying to break into your hand gets him nowhere, but if he takes a step back he gets yummy cheese. If he over mouths your hand while hes learning or gets too over excited a firm no will get him back on track. Once he learns his nose cant touch your closed hand when you're holding food you can tell him 'stand' followed by 'leave' so that hes standing very alert with your hand just infront of his nose. Once you have that you can slowly increase the distance your hand is from his nose. If you have already taught the word leave as a no you cant have that come back here, use wait instead. Well you could even teach him to 'carrot' or 'piano' if you like, as long as you use the same word every time!
For a stacked breed you could try the leave command as above, but without increasing the distance between the dog and your hand. However someone who actually shows a stacked breed may have better advice for you.
Thats the fun of puppies! If I ever have a 'you're just not getting it' moment I go and watch a ring of Gordon Setter puppies. Those nutty clowns never disapoint!
As above, yes puppies should be puppies! You may well find your boy will have a long lasting love of showing as its clearly so fun. Whereas the 'perfect' older bitch may well tire of the whole showing lark after just a few years.
Enjoy!