Not sure why you want to control volume.  Is the pipe capped so that only the 2 inch hose will get water ?  How many gallon per min is the well ?

I filled water tanks from a 800 gallon well on my pivot by just tapping into a 4 inch inspection hole on the top of my chemigation check valve.  I was not to concerned if I spilled a little water.  Maybe you need to be more careful with you filling  process.