I would get them to try first without a partner. I think of it as 1 step to move, 2 to change direction.
So all stand in big circle (not holding hands).Start with R foot. 1 step sideways, 2 steps on the spot, turning. You will be facing out with weight on R foot ready to start again with L foot.
Now waltz round the room (anticlockwise, but turning clockwise)to the music without a partner (no overtaking).
Now with a partner, the one with back (dancing as man if you have mixed couples) to centre starts with L foot. Without the music, then (after you've unplaited your legs) with the music.
You will already know that the music is not played at the same speed as a ballroom waltz

Simple.

Hope that helps