small dogs can be trained just the same as big dogs. There are other types of corrective collars/harnesses that can be used. There is the haltie and gentle leader. I just use a regular ol step in harness. morgan is well trained (except at the dog park

). she walks well on a leash, either right next to me or a step behind me. she can sit, stay, come, lay down, give paw, roll over, play dead, high five, etc... i can put her in a down/stay and then walk 50 feet away, wait 30 seconds and then call her to me.
at the dog park though she pretends she can't hear me

especially for the first 30 minutes of being there. once she calms down and has smelled every dog, leaf, rock, and fence, then she'll listen to me. hehe