Has anyone used anything like this? What product do you recommend? Any pics of your work?

 

Hey there, a friend of mine used to run a business offering this service, mainly to large fleets and taxi drivers.
Full service meant removing the wheels etc and a full undercoat of the spray on the underside protected it for years to come against the harsh winters / road salts and rust etc etc.
I'd say its well worth doing if you intend to keep the car for some time and can get a reputable operator to complete thew job at a reasonable price.

 

One bit of caution though, make sure that the company doing the coating either has an additive in the coating that will stop any rust that is currently on the car or that they will wire wheel/paint those parts that are currently rusty to prevent them from continuing to rust. By spraying the liner on there, you can trap all the bad stuff there and actually make things worse