The foggers I ordered just have arrived, and I love them. I tried them out almost immediately, you have to fill it up with a destilled water, using a syringe, with the needle part on, since the load opening is too small, for the dropplets to enter.
With one load it can work for about 5 minutes.
There is one thing that I figured out, the flexible lego pneumatic tubes can perfectly fit in the loading hole, so now I try to figure out, how could I make a built in loading mechanism for my MOC locomotive.

Works great to create steam engines.
Just make sure you use destilled water!

I love the fogger brick, as the effect is great for steam trains. But there are some thing buyers should know.
The device activated as soon as connected to the power function 9V. This is ok for the on/off style PF but not if you use IR receivers, as it will have no effect. You need to solder it to C1 or C2 pin to be able to steer it and adjust the steam setting via IR remote. Also there is no pipette included to inject the water into the tank. The water tank is the small hole, not the large one!

1PCS Fogger

Great product, best support! Totally happy 😃