i've never actually seen these systems up close, but i guess you've got a fill and dump solenoid for each wheel? I think what i would do is first is figure out how much current these solenoids will draw if you are filling all four wheels at once. Then i would wire in some power with appropriate gauge wire and make sure the circuit is fused. Then i would split the power to four single-pole double-throw momentary switches. Then i would run a circuit to each solenoid. With the momentary switches you can raise or lower each wheel.
Hope this helps.
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