It sucks in pulses like a baby sucking a nipple. It has a speed control. The faster it sucks, the harder it sucks. It sucks your cum through it and deposits it in a baby bottle that screws onto the pump.
Until I saw this I wanted to try a cow milking machine. This seems like it would probably feel kinda similar. Now that I see this I may try a breast pump first since they can be gotten cheaper anyhow. The pump that does all the work can probably be modified to work with a different tube. I would just make sure that whatever I do to it, the bottle can still be used to collect the cum so that I would be able to keep it on and not have to clean it out so much. Some who use one like this might prefer to let it suck for as long as they don't need to leave their house. I would use it even after I have cummed too. Just let it keep on sucking my cock hard or soft. For that find a comfortable but easy to wash chair to sit in. Easy to wash because it may eventually need it.
It would be fun to get tied down and left with it sucking for hours and hours and not know when the machine will get turned off. I would love to find a slave with a thick but average length cock, maybe an Asian boy who cums huge loads regularly. I would want to make him and all of his friends my cum cows to milk relentlessly. Maybe even use cow milking machines and similar things on them. The pump you use looks good sucking a cock
I often let it suck my fat cock's swollen nob into it and sucks, and sucks, and sucks making me cum over and over! Even after there is nothing left to squirt!
That would be good for seeing how much milk you produce in a night of milking. If I had one of those or a cow milking machine I would be using it on my self a lot.