I have a JD4440, with only 2 remotes, but run each Hydraulic boom separate.(also have power beyond circuit, on this tractor) 

I have power beyond, with a manual external  needle valve control, and it runs the hydraulic flow to the sprayer pump = I open it enough to get 52-55psi, for chemical pressure; then the 2 levers, inside cab while operate the booms.

Disadvantage to this setup, is once chemical gets very low, I have to quickly jump out and shutoff, the manual power beyond circuit, so I don't "hurt" the sprayer pump by running it dry. Just changed sprayer pump, last year; but was in a hurry, so I bought new. BUT I did reseal old pump, when I had more time. {Note old pump was on since 2012, and it was used even back then.}

My booms were already hydraulic, and it is a 60 ft X-Fold unit.