89er,
A can of brake parts cleaner should blast off any oil or grease, but glasses and gloves are a must.
(The Chlorinated stuff is best but it is bad for you!)
Then after the pads are mounted & bled finish with the alcohol.
I reckon there plenty of other things you could use to clean the pads and rotors with, but this works for me.
Save an old windex bottle or the like to pour the alcohol in
(it's easier to spray, instead of wetting paper towels or rags etc )
The last thing I do before I put the bike away after cleaning is Spray and wipe the rotors also.
The soap from washing, lubing the chain, wax, etc, will build up and add to the glazing.
It sounds like a pain in the butt, but after a few times it takes probably 15 seconds or so per side of wheel.
Just another part of the Routine.
Tuck\o/