This may sound dumb, and I may have read your post wrong, but you are having trouble getting it to cast. Is the toon on follow stopped, because if you press it too soon (i.e. first toon stopped, second toon still catching up) then only the stopped toon will cast and the second toon will wait until the next round, after he is stopped.

As i said, may sound dumb, but I kept forgetting to wait for the second toon for a while