At 4 months the martingale is great. Leave the prong off for another 6 months at least in my opinion. If you are looking to train in schutzhund have you found a club yet? If you have, does your trainer know about this puppy class? There are no "puppy classes" for schutzhund dogs, they pretty much get to chase rags and tugs and be goofy puppies. Inductive O.B., drive building, focus work, and FUN.