Sometimes it helps to give directions, count or talk gently in the rhythm and tempo that you want while the music’s playing. This gives pianists a rhythmic framework within which they can feel freer to be more expressive, because they’re not having to concentrate so hard on keeping the rhythm going. You can then use your voice as a means of controlling the tempo of the exercise in subtle and expressive ways, because the pianist will have locked into the tempo of your voice almost without thinking.
