Yea, that's probably the best "english translation" I've heard. The "oo" in Coop is long and deep. Although I have a bad habit of saying it with a short "o", like in "Soup". And yea, you're not supposed to pronounce the "s" in Migros either, but I still do that too, even after almost 10 years here ...bad habits are hard to break I guess...
Pretty sure I've heard it pronounced without the hyphen...but akin to the Dutch way of using vowels...i.e. just an elongated sound.
So not 'koop' (as in chicken coop)...but 'kohp' (as in the 'o' lasts longer. Still single syllable tho').
But then it depends which Swissies you knock around with or whether perhaps you're speaking to an Auslander. Everyone speaks better German than me, so it's sometimes hard to tell who the natives are.
My Swiss friends are Basel natives and say Co Op - two syllables. I was telling them about this discussion last night and they were surprised at all the variables, although understand if the speaker is French or Italian etc. But they definitely don't say 'coop' as in the English 'chicken coop'.
For the exact same prononciation, some people will discribe a long o, others will discribe two syllables. I remember my courses of acoustic phonetics, we went mad trying to discribe sounds, it all looks scientifical but at the end of the day, it's all perception put into scientific categories by human beings. An experience in linguistics that fascinated me: Germans asked if they hear i or ü in the word wirklich, some people say i when the whole word is pronounced, they say they hear ü when the sound is isolated from the other phonems of the word. Others the other way around, yet others twice i and the last group twice ü. Complex...
Colours the same: for the exact same spot on the spectrum, some people see green others blue, even if they are same mother tongue speakers and same age. People asked to circle the surface typical for a colour, the result are stunning: not everybody have the same perception of frontiere between colours (especially green/blue and yellow/orange, others are clearer). Complex...
Linguistics teaches you so much... how do you live without?