Yeah, I think that works. Not sure it is worth it though. Have you seen the tests comparing foams against soap and control? Few have a small effect. IMO it more of a guide to make sure you rinse every inch with the pw. And that helps a lot, but I don’t need that. Like Mike said, suds might suspend solids that you then press against the paint. It may or may not happen. I rather consciously power wash every inch. Then again, if it works for you, keep it up. Looks (an feels) very cool.
For me, I never use a foam cannon. A dozen or so edgeless mf in a soap bucket and after using on a panel it never hits the soap bucket again.