<<"The towns seem fairly close in proximity...Herbligen, Buchholterberg, Oberdiessbach etc.">>
Oh yes, now I recall the earlier thread.
The work that Alpenrose posted on using local transport seems reasonable to me in light of your goals. Alpenrose likes to make use of public transport, knows how to do it, and with good reason. It is very effective.
A map was included in that earlier post.
Has your available time for the quick visits changed?
Langanau i.E. was included. It is not on the list of three you just presented, and it is the outlier in the earlier post. If you chose not to include it, you could easily fit it into a half a day, using buses.
Here is a bit more information about buses. In this link I have zoomed in to a map of the region and turned on the icons for bus and train stops in the Menu, under Points of Interest/Traffic.
Zoom in and out, and, if the icons are annoying, go to the Menu/Points of Interest/Traffic and check or uncheck the boxes for trains and buses.
If I were doing it with your constraints as originally mentioned by you in your post and discussed then, and, in fact, asked about - I'd think that renting a car makes a lot of sense. That is what I would do. I'd rent at Bern/Belp Airport. It is within about 10 miles of your area of interest.
It would almost certainly be cheaper than hiring a guide. If you stay in the area, you could leave your luggage at your inn.
You can also leave luggage at the airport:
www.google.com/search?q=lockers+luggage+at+B ern+Belp+airport&clien t=firefox-b-1&tbm=isch&tbo=u&sourc e=univ&sa=X&ved=0ahUKE wjGx9WdgtXaAhVP0lMKHc7 IAhQQsAQIgQE&biw=1560& bih=925
Thun Tourist Info could likely help you search for a guide. I've not used that office, but, in general, those places are really helpful.
<<"Is it possible to hire a local person for half a day to drive you to
these small towns? Definitely would want to make sure they are a
professional guide of some sort (not just a random person looking to
make some money.)">>
That made me think a bit. Locals often know a lot about family histories. The families have been in the rural regions for a long time, and are frequently connected by marriage, church membership, Jodlerklubs, political parties, etc. There are many farmsteads in Switzerland like yours in Missouri, but they may go back to roots older than the country of the USA. Do you have any distant cousins there? They might be able to point you to someone who can help you. They might even want to do it themselves, although I'd not actually ask anyone to do that. They could always volunteer. Many Swiss have excellent English language skills. And, I've found many people, while chatting with locals around the country, that have stayed a few years in the USA at one time or another. They like to help travelers, especially those who display interest in the local history.