Never change your target ever again, while healing and smiting!
#showtooltip Holy Fire
/cast [harm, mod:ctrl][@targettarget, harm, mod:ctrl][@focus, harm, mod:ctrl][@focustarget, harm, mod:ctrl] Smite
/cast [harm, nomod][@targettarget, harm, nomod][@focus, harm, nomod][@focustarget, harm, nomod] Holy Fire
Press the button while having anything remotely related with an enemy targeted to Holy Fire them!
Press Control+button to Smite!
Mash that buttons and watch as stuff magically (it really is magic) dies!
PS: Most priests only have time to actually Holy Fire every 10 seconds to keep up Evangelism, so I put Holy Fire directly on the button, despite it being used less than Smite. If you're a priest with a lot of smiting, you may change all "nomod" to "mod:ctrl" and vice versa.
PS 2: If you need further customization, please request it in this thread.