I bought a very cheap Bellababy breast pump (BLA8042) for under 10 bucks from the second-hand market, and wanted to share my experience with you.

On the one hand, I wanted to automate pumping and on the other hand, I wanted to take advantage of the benefits of pulsatile pumping. I have modified it accordingly with little effort. I can also document this specifically for this pump on request. It's really quite simple.
These types of breast pumps all work according to the same principle: They suck (one or several times depending on the program) and release the pressure via a valve (second tube on the pump with the hose clamp).

First of all, the desired pressure must be achieved. To do this, the valve must remain closed until the desired pressure (e.g. 3hg) is reached. Then you open the valve VERY SLOWLY until the pressure drops to e.g. 2hg.

If the setting is correct (you quickly develop a feel for it), the pressure will now always fluctuate between 2 and 3hg, as in the example. The size of the cylinder determines how large the pressure difference is between suction and discharge. The larger the cylinder, the smaller the difference ( e.g.: With a 5L cylinder, it is approx. 1hg. With smaller cylinders, it is correspondingly more, with larger ones correspondingly less).
According to the manual, the battery in this pump lasts approx. 4 hours, which is sufficient for one pumping session. In principle, however, the pump should be able to run for longer with the mains adapter or a powerbank plugged in (I haven't tried this yet). It should also be noted that the programs end automatically after approx. 30 minutes. This means that the pressure in the cylinder is suddenly lost after this time. You can use this “pause” to change the water, move around, get something to drink, etc. If you set a timer, you can also prevent this by closing the valve in good time and simply restarting the program before it runs out.
I recently subjected the whole thing to a practical test and have to say that pulsating pumping is much more efficient than just keeping the pressure constant. After just one hour, I already had the results that would otherwise only appear after 2 or 2.5 hours. Perhaps you can also pump with a little less pressure, which may be better tolerated by some people.

According to the manufacturer, the maximum vacuum that can be generated is around 10 hg. There are a total of 4 programs, which differ in how often and how long the suction cycle is until the pressure is released again. I have had the best experience with program 4 (deep mode). There are 6 intensity levels. It is best to set this to the highest level to achieve the vacuum as quickly as possible.