To paint or not to paint the underside

i own a media blast company and have done tons of floor pans. To dispel some myths first thing. media takes off undercoating no problem. if you are using your 2hp shop compressor and your $79 harbor freight pot...maybe not. scraping some of it first does make the job faster but i can do any floor in an hour-ish. dry ice may or may not take off rust and the cost is probably 4-6x that of dry media. wet blasting is shite on cars. it just leaves mud in places you cant get to and it 100% does nothing more than dry does do other than reducing dust. i own two wet set ups for brick and concrete....not cars.

in my opinion your best option is to have a portable guy come and blast the underside in your driveway.