the system is pretty easy.
To cure it would be /ac "Cure" <st> this will let you select which npc to cast on.
because all your timers are on screen, it is a lot easier to track and click them from the bar though, IMO
Something I do is press f1 through f8 first to target the correct people then click cure and press enter,
Some people lock in a special cure just for the tank and edit it every time the party fills up so it always cures the tank,
example
/ac "Cure" <p3> where the tank is 3rd in the party list on the screen. hope this helps.

/ac "spell in game" <p0-p7> or <t> or any of these
<t> Displays current target name.
<me> Displays your character's name.
<p0> Party Member 0. Displays your character's name.
<p1> Party Member 1. Displays name of first party member in list.
<p2> Party Member 2. Displays name of second party member in list.
<p3> Party Member 3. Displays name of third party member in list.
<p4> Party Member 4. Displays name of fourth party member in list.
<p5> Party Member 5. Displays name of fifth party member in list.
<p6> Party Member 6. Displays name of sixth party member in list.
<p7> Party Member 7. Displays name of seventh party member in list.
<st> Subtarget.
<stpc> Displays available PC subtargets.
<stnpc> Displays available NPC subtargets.
<stenemy> Displays available engageable enemy subtargets.
<stenmity> Displays available engaged enemy subtargets.
<stparty> Displays available party member subtargets.
<lastat> Displays the last enemy that attacked you.


P.S. let me know if you try the class gear job changer thing, i thought it was cool and frees up 7 macro slots plus changes in a 3rd of the time.