I've had mixed results with this. In some cases, it's worked better to break a task up into single pieces and call several spirits up or even just telling several spirits the same thing. In others, nothing really came of it and for others, I just used one.
So, which have you guys found works best for you: calling one spirit for one overall job or choosing several spirits yourself for one overall job, whether or not it takes longer with one way or the other? I'm wondering about accuracy and how on target it ended up being. While speed is an issue, it's not the only one.