We found we often had to just do piecemeal searches, a combination of zillow, craigslist and just driving around the areas we wanted to buy in.
In a perfect world open houses would all be scheduled ahead of time, but there were inevitably homes that popped up the day of, and sometimes those were the best we saw.
As a general word of warning: Open Houses can be useful to get a feel for an area and what you do and don’t like. But beyond a first “debut” open house, there often has to be something wrong with the home or the pricing for it to go to a second, third, fourth open house. In this fairly balanced market reasonably priced, well maintained homes sell fairly quickly. A lot of the best homes we saw never went on open house.