I was told by an instructor to dance Int. waltz or other int. dances only for about a year or so and then go back to American Smooth. One's technique will improve and will carry over to better smooth. It is easy to get sloppy with American Smooth and all the open work.
The typical Int. Waltz routine that I do: Natural Turn, Closed Change, Reverse Turn, Whisk, Chasse from Promanade, Hesitation, Progressive Chasse, Back Lock, Outside change, Spin Turn, Double reverse spin turns, Weave, Impetus, Reverse Corte, Back Whisk and start over. There are parts of the routine that moves, but some with the foot closures feel like I am not moving much. However the technique on all of this has to be precise or you will hurt your ladys back and things will fall apart quickly. Int. Waltz is very challenging, more so than Foxtrot for me.