Can I use a pancake compressor for spray painting or impact tools?

Reviewers on r/Tools and bobistheoilguy.com are blunt: standard 6-gallon pancakes don't deliver enough sustained CFM for HVLP spray guns or impact wrenches. Several threads specifically warn about the regulator on the Porter-Cable struggling to hold low spray-gun pressures. For those tools you want a larger tank and higher CFM rating.