Two things you want :
-Watch the cooldown
I would use class timer, just make your HoS target your focus and make sure your focus bars are enabled
-announce to raidchat
/in 12 /raid Hand of Sacrifice expired
Found this on wowwiki under "Useful macros for paladins":
Code:
/clearfocus [modifier:shift] [target=focus,dead] [target=focus,noexists]
/focus [target=focus,noexists]
/script SetRaidTarget("focus", 1)
/cast [target=focus] Hand of Sacrifice
a simple macro would look something like this:
/cast Hand of Sacrifice
/focus
/ra Hand of Sacrifice active on %t
/in 12 /raid Hand of Sacrifice has expired
btw in classtimer you can also enable somewhere that if you shift click on one of the bars it will display how much time is left on that ability
ex: "/p [buffname](player) has xx [time] left "
you can change the channel to post it in