Hi. Could do with knowing what

-Grind: coarse or thin
-Roast: Dark or Light
-Variety: Robusta, Arabica, etc..

makes the Best Coffee for cold-brewing.

I am currently using Cafe Bustelo "Espresso" Coffee.
It is is OK, but not a patch on Illy and other brands I have used before.
Is there an "off-the-shelf" brand that is particularly good for this?

thin, dark, french roast

eight o clock is excellent