Starting out with double priests, need some pointers for a first timer

[Maexxi]

Hello! This is my first dual boxing attempt, and so far its been quite successful :] I chose dual-priests, and will be speccing them both shadow to take advantage of the synergy.
So far for the first few levels I basically mirrored them both, so they would be casting the exact same spell on the mob, and healing themselves at the same time. I found this to be very mana intensive, cause sometimes one would be over-healing themselves, while the other maybe dying. While this is probably the EASIEST way to start out... I'm thinking in the higher levels, I may need my slave to heal my main or vice versa.

SO! I was wondering if anyone could help me out with some macros. Is there a way to write a script that would command my slave to dps (ie. smite) but add a condition to the macro like it would cast lesser heal if my main is low. Something like that I guess. What's the most efficient way to level dual priests? Any kind of insight or suggestion will help! Thanks :]

[Charm4sho]

erm.. just a idea but..

button 1: mindblast on mainchar and renew,flashheal or bubble on slave
button2: mindblast on slave, and renew,flash heal or bubble macro for main

should work since you dont use mind blast evry second and you dont need heals each sec :P