Buses start running around 6:15-6:30. They are intended for those guests with early morning ADRs. So...for a 7:45 ADR, at CM's, coming from CBR...be out at your resort MK bus stop by 7:00. The buses come less frequently than regular park buses, so if you just miss one, you may have a longish wait. I would be out closer to 6:45 but I tend to be a wee bit obsessive. When you get to the MK, you can either take the monorail or walk to the CR. The walk will take you about 8 mins, along the sidewalk that runs beneath the monorail line. If you take the monorail, you will have to walk about 5 mins, in the other direction to the monorail platform and then wait for the resort monorail to get there. It should take about 4 mins to get to the CR from MK via the monorail.
I usually just walk.
You should be out of CMs within an hour or so...walk back over. If you take the monorail, it will take you about 20 mins...it takes that long to get to the MK from the CR. Walking is much faster.
Now...for an 8:10 ADR at Crystal Palace, be out at your bus stop by 7:15 at the latest. Why?? Because that bus will stop at the Dolphin, possibly YC/BC and maybe BW. It may have already been to BW before heading to the Swan...that is the usual route. But, it will do to the Dolphin. Sometimes those early ADR buses will stop at YC then the BC..this adds about 15 mins to the time of your trip. When you get to the MK, just head over to the left side of the turnstiles...you will see a CM with a clipboard...they have all the ADR confirmations numbers and will direct you into the park for your breakfast.