I'm getting around to sanding down my bodywork to do a paintjob and would like some advice on what tools and techniques would make the job easier.

The bodywork has a flat black textured coating on from using truck bed liner, as well as platic weld from doing crack repair. I want to make it smooth.

I have already a vibrating sander (black and decker drywall type), a B&D roto tool (cheaper than Dremel, but same thing), a drill and ME (but I'd rather work smarter than harder, I probably need to do the entire body).

Please provide suggestions to make this go quickly and painlessly.