To effectively have a small production line you need to have 3 pieces of equipment/processes.
First step is using a stencil to apply solder paste. this can be done with a stencil alone as a mask on top of a PCB, but a better way is to use a 200.- USD stencil printer. This pic show a low cost one for ca 150.- USD.
Second step is to use the pick and place machine to add components.
The last step is to put this into an automated reflow owen. I actually have one of these, but have not used it much because I solder very fast with a heat fan.
I have 2 reasons for wanting to start using the stencil. It is faster and easier to add correct solder paste, and by using the owen I avoid the number of cold soldering problems I have.
I just assembled a wifi board and sat hours fixing 2 cold soldering – soldering that look perfectly ok through a microscope, but actually is not connected. These problems take time and the first step in improving is to actually use stencils and the owen while I ramp up for a full production line.
The drawback is that a PCB that usually cost 5.- USD now will cost 50.- due to the cost and P&P for a stencil with frame.