During my last ortho visit, my ortho (who I adore and is really invisalign-experienced) told me to chew freedent gum for an hour each day. He said some patients of his have been doing that and it really stimulated tooth movement and seated the aligners well.
I decided to do it on the 2nd day of aligner 14, which I'd thought wasn't fitting well, and he is so right! My teeth moved VERY quickly this time and the aligners are perfectly seated now. It doesn't stick to the aligners so I figured I'd pass the tip along. Added benefit of less dry mouth and fresh breath.