I can remove buffs yay! So how do I ADD them in the first place?

I'm sure plenty of you people out there have wanted to add buffs like dizzyness, slow, etc. to units without having to manually cast them the ghetto way. So, for those of you who know, how DO you add buffs? Using custom abilities and triggers? If there is an ez solution, I'm all for it. If that is somehow not possible, has anyone gotten the Unit Order trigger for spells to work? Ex: Unit Order Archmage to Cast Blizzard at Target.

create an invisible casting unit and order it cast the ability on the unit in question then remove it thereafter -- thats the only way i know, but most my maps don't require that, so i'm not up to date on the various ways of accomplishing the task