Years ago when I was experimenting with the prevention of mold, I used an ultra sonic bath to clean batches of cuttings. I laid them down horizontally in the bath. And I tried using plain water, an alcohol/water solution, and an AB Dawn solution. They all cleaned up nice by the mechanical agitation of the sonic waves. The Dawn solution seemed to work the best. I'm guessing that is because of the surfactants (ie. Chemical wetting agents) that are in the detergent. Using an ultrasonic bath adds much more of an intense and reliable "mechanical cleaning" action to the cleaning process. Using AB Dawn and then 10% bleach "chemically" cleans those cuttings too. The combination of excellent mechanical action AND chemical cleaning gets them pretty clean.
However, from a practical standpoint.....using a toothbrush (i.e. human mechanical action rather than sonic action) and cleaning sequentially those cuttings with Dawn AB soapy solution that is then followed by a brief minute soaking in 10 bleach solution.........works quite well for the needs of most people. In short people don't need an ultrasonic bath unless they really want one.
FYI, I also used UV light to treat my cuttings. This works great too. Years ago , I was big time into developing a safe "Anti Mold" chemical agent. To conduct my many experiments, I needed lot of both moldy cuttings and cuttings that were very clean for my studies. I leaned how to make batches of moldy cutting and found some effective chemicals too. In fact I had even named my product ----Mold X2. LOL.....
However, that extreme cleaning is simply not needed "if" you pay attention to the rules of rooting cuttings. First and foremost......never apply heat intentionally to cuttings that are in a "closed" rooting environment. This can easily form that bad ass high purity "condensation" (again not talking tap water here) can form on any newly opening buds or on any newly formed roots. This can initiate an osmosis reaction that will liberate food for mold to grow on. Condensation is what most often begins the mold/rot cycle and it is caused by a temperature differential that exists anywhere in the "rooting environment".
But I have to tell you this......it is sure "fun" to use heating mats, propagation mats, ultra sonic baths, and ultra violet lights on your cuttings!!! But NONE of that is needed to attain a very high success rate of turning twigs into plant-able fig trees.
Have fun with your experiments too.
If you switch over the cuttings that you already started to this rooting method, let us know how they progress for you. Try it with half to be on the safe side. Best of luck to you.
Dan
Semper Fi-cus