There was a time that a restoration ended at the rockers. Even in decent quality shops, vehicle refinishing below the doors left a lot to be desired. It was not uncommon to see repairs left undone, filler left unfinished, primer spots and even a lack of paint down low on cars. Nowaday, if the shop you take your vehicle to doesn't have some way of lifting the car up to eye level, or of tipping the car over on it's side, I would suggest you walk away! There's just no way a man on a creeper, or piece of cardboard can do the work down low to the same quality as when that same area is easily accessable.
While the rotisserie is one tool that allows full access to the underside of a project is it by no means the only one and - arguably - not the best tool in every situation. Have a look below at the myriad of ways people have thought of to gain access to the underbody in order to treat these important parts of a restored vehicle.
Here's the link to my post on Garage Journal.com. It has a lot of great ideas, in addition to the wooden tip-over style: Rotisseries and tip-over jigs