I'm using a single keystroke, mapped in ISB with multiple steps to cycle through the buffs (Priest, Mage, Pala), step by step, including group and single buffs.
Plus a secondary key to buff up a single target with all buffs at the same time.

At the beginning I did it like Ughmahedhurtz, same key in the client + broadcasting it / using VFX + clique but IMO thats far less convenient.