Rather than just typing how they look, here
is a listing of about a third of the county road signs in the state. The others are also on that site if you wanted to look, but basically you have A2 through H63. The signs include the county and the letter/number designation, when there is a sign at all (county road signage in Michigan is generally very poor). The state is divided into regions, where each region gets a letter A-H. Then, a number is attached to refer to the individual road.
As far as postal addresses, I tried looking at locations around some of the county roads and the addresses are all based on the road name rather than the county road number. This seems to be true even for many addresses along state roads, such as addresses on M-119 being using the street name of Lake Shore Dr. In almost all, or perhaps all, cases in Michigan, the county road designation is an alternate name and not the main name of the street, so there may not be any addresses that use the county road number. I can't easily verify that, though.
As far as the - between letter and number, I think it's fine for that to go. The signs don't have it, but any names given for the roads anywhere other than the signs uses it. That may just be for readability rather than being official, though. In any case, B15 is just as good for directions, both visual and verbal as B-15 and is probably slightly faster in the TTS because of the extra pause for the dash.
And I wasn't meaning every state should drop their naming conventions, but just that I think it helps to avoid confusion if they were all to use something like CR- or County Hwy in front of any county roads. It wouldn't matter how they label the roads (letters, numbers, letters and numbers, etc.) because it would still look and sound okay. I wasn't really expecting that to happen. It was just an idle comment.
There is also potential for the name to be read wrong if the letter is at the beginning of the street name. I'm not sure if the dash prevents that or not as I haven't tested it. What does it do for state roads? For example, if it's labeled just "PA-1", is that read "P.A. 1" or "Pennsylvania 1" or "Pa 1"? If it tries to convert PA to Pennsylvania, there could be potential for A, B, C, D, E, F, G, or H to be converted into something by the TTS as well, which would mess up the verbal directions. I don't know if that could be a problem today or could potentially become a problem later or if it will never be a problem. I just thought I'd mention it just in case. I believe if the letter is in the middle, it's treated differently, but maybe I'm wrong about that.
One thing we may need to also consider when naming these... There are roads in Michigan called County Road XXX that aren't county highways with the special signs. They are just regular roads with that label unless I am mistaken. I think the difference between them is perhaps a matter of whether they are inter-county or inner-county. The inter-county ones have the special signs. It may not matter and we could potentially call all of the CR-, but I don't have any experience directly with any of the roads labeled as County Road XXX. I only have direct experience with the ones I mentioned that have the A-H region designations.