Sorry. I have seen the "flow testing kit" advertised. But for those who intend to save the money of a kit, here is the setup commonly used.
http://www.model-a.org/jet_flow_testing.html
It basically amounts to a controlled "head" of fluid, and timing out the flow into a graduated cylinder. The only technical challenge is creating a repeatable "head" which is what the reservoir accomplishes.
It has been addressed in the literature as well. Tom (above) has contributed to the literature.
https://www.brattons.com/media/wysiw..._-_11-2007.pdf
And - while original numbered jets provide SOME assurance of actual flow, only an actual test can assure positively. Original jets can wear, and they can have "deposits" from the gas.
Joe K