Its pretty simple, you turn a knob on the bottom of the shock, there is an arrow on the shock that points to the number you are set on. it goes from 1 to 9, 1 is soft, 9 is firm.
On my truck it takes all of 2 min to do all 4 corners, but thats because I have 6" lift and 33's, jack stands hardly reach the frame anymore and I can drop the tranny without jacking hte truck off the ground. ON a lowered truck you would have a good bit of crawling to do to access all 4 of them.
Zthe in cab controller works but it is a waste of $$$ if you ask me, although alot of full size truick guys use it for towing and it would work good on a lowered truck, its just alot of plastic air lines to run and for me just one more thing to get snagged off road.....
You might also consider the Bilstein shocks, no need to adjust, ever. I like the adjustability of the Rancho's for my needs, even if its just from 5-7 on the back two for when I hook up the boat......