I am looking at using "Monstaliner" (tintable undercoat) roll on finish to paint my entire Ranger, has anyone tried this or anything similar?

 

Why on earth would you want to do that?

EDIT: I saw a Dodge RAM painted with bed liner (don't know what brand). It seriously looked like ****.

 

x2 with mhoward... under the truck, on the rocker panel area, maybe, they do make Rock Guard for that but !

Why would you want to do it anyway ?

One thing to consider with a bed liner/undercoat is adhesion of the paint, it needs a good surface, rough but not too rough, and a good base paint.

Talk to a paint guy and see what they say, I am not saying don't do it, just do a lot of checking before starting the project; you could end up with a mess the will be a PITA to clean up !