[gumbysuz]

I am surprised your trainer recommends a pinch collar for a yorkie. I have trained half a dozen yorkies with harness only. It's about positive reward and expectations. As my husband likes to point out, he was harder to train than Dori. If your yorkie pulls excessively on walks, there are harnesses to correct that. But, still, it starts with the owner.
Good luck with your training and crate safety.