I hired one which was mentioned in a previous STW post from fatlama. Worked out at £20 for a week.
I picked a local 2 mile loop with a bit of everything on it, some climbing, some drops and jumps, some rough stuff and some fast flowing bits. I rode this loop and adjusted things after each lap until everything was in the green zone.
I made a note of these setting and now just work from these if I visit some where vastly different (uplift etc) otherwise these setting are fine for most of my riding.
I think it helps you focus on what your suspension is doing and what effect all the knobs and dial have rather than giving you the perfect setup.