Communion question.

[GrudgeBringer]

I have been getting into communions and keep coming up with little things that I don't find covered.

Say I have 18 Mystics and I want to make 2 communions of 8 each.

I understand how to set up the first one (where the CM has to be the last one to cast), but how do I set up the second one.

The only way I can see around this CM casting nullifies everthing after it.... is to have all 16 CS in an order and then have the 2 CM on the bottom and the game will automatically aassign the first 8 CS to the first CM listed and 8 to the second.

If this is the case how would I go about setting one up with 12 mystics and 1 with 4?

I am I just missing something that is easy?