The way you're supposed to think of cleaning is that all of it is cleaning. the first bath has chemicals to dissolve the oils Remove oxides make the plates bright put things into the solution make things clean overly simplistic probably but it cleans. The rinse also continues to dissolve things into the solution and is technically cleaning. The other thing it is doing is reducing the concentration of the original solution. Which is why typically a cleaning solution followed by two separate rinses unless looking at the modern machines that might have three rinses.
If you notice up above nickelsilver Posted that he's using isopropyl alcohol is his rinse actually has two of them. Then looks like were similar for clocks in that I use a commercial solution and follow up with hot running water then immediately in the alcohol. But I still don't have enough experience I've only cleaned a couple of clocks. Then it looks like the demineralized and distilled water is basically just really really clean water. Depending upon where you live the quality of water and its impurities plus the fluorides chlorine might be a problem.
Then as far as ultrasonic goes it really doesn't have to be fancy. I started off with a small machine purchased from the drugstore don't think it cost very much money has really surprise was like why Outlook it's 20 and $30 like a century ago or something. Specifically designed where you're supposed to put a beaker into the ultrasonic which today everybody frowns on you shouldn't have anything directly on top of the transducer there should be a separation as bad things will supposedly happen. Except that machine ran for I don't even remember how many years a lot of years before it finally disintegrated. So it didn't seem to suffer any problems of having a beaker directly on top and then surrounded by water to couple the energy. Now if you scroll down the page at the link below I'm using a bigger ultrasonic and to keep everybody happy and not fuss the beaker is on something above the transducers surrounded by water.
Yes, It is very helpful in determining authentic GI issue watches. There seems to be a cottage industry of fake military watches. Mine is 100% authentic thankfully. I do wish I had the original carboard box it came in. I nearly manufactured one from scratch, but I gave up when I saw the work involved, lol.
BTW... The photo I posted of the dial looks awful... Specs of dust on the Crystal