when you glitch andy / meph do you need ZERO mf ?

or is it just not required?

Not required

The more MF you have the less Rares will drop.

when you get quest drops, all items are upgraded to minimum rare quality. Your %MF just affects the odds they will upgrade to set/unique, instead of the normal magic/rare/set/unique tables
So the amount of %MF you want depends on what you're trying to find. If you're farming NM andy for SoJs, you want as much %MF as possible because you want to get unique rings, not rare rings
but if you're on classic and farming for rare armor pieces, you can do 0% mf just fine, because the sets/uniques (other than soj) are worthless in classic