I have been in practice over 20 yrs, 10 of that solo. I get around the overbook problem by leaving plenty of open spaces in the schedule for same day appts. In the winter, we increase the number of spaces we leave open for same day scheduling. Most of the 3-6mos regulars book their appts ahead so the staff can achieve this. I have never taken Medicaid, so I cannot speak on that.
I do utilize the ER if I think that the pt will need stat labs/xrays/IV fluids. Plus, my area is saturated with UrgentCares so people are not forced to the ER after hours.