I don't know how useful this will be for anyone else, but I play using the default UI action-bars, using shift-(1-6) to switch between them. So, for example, frost shock is on bar 3, button 8, so I press shift-3-8 to cast it. Earth shock is on bar 1 button 8, so I could then do shift-1-8 to earth shock (when it was off cooldown). It sounds a little clumsy, but it's how I've played since beta and works very well for me.

On my multibox setup, in general, buttons 1234567 are for the paladin, while 890-= are for the shammies. The shammies have nothing at all on most bars in the 1-7 buttons.

If you happen to use a similar setup (via Nostromo maybe), you can download this spreadsheet that I made when planning out my multibox setup. I think I've moved a couple of things around (seal of wisdom is not on there) since I last updated this, but it's mostly how all my bars are configured. You'll have to fill in the blanks a bit in terms of macros; for example, 'dtotem' casts either grounding totem, tremor totem or stoneclaw totem (using a rotating cast-sequence macro so that I can stagger them), depending on whether I have ctrl or alt pressed.