And I kiss for canter
She generally responds well to these. To change gaits slower I usually begin with aaannnnddd trot/walk. It took a little while for me to figure out what worked for her, but when I did this it was obvious that she understood and was very familiar with it.
My MIL gets so irritated when I don't use "WHOOP! WHOOP!" to slow her down. She will even yell it when I'm longing, sometimes from across the pasture! Of course that's when I get irritated, but that is for another post!