I have used gumout for decades, followed by compressed air. There is enough pressure in the carb spray to rinse out the passages real well, and the air finishes it off. I repeat this process until I'm satified the carb spray comes out clean. I spray both ways on each and every passageway.
I visually observe the pattern of the carb spray coming out air bleeds or accelerator nozzles, and have been able to spot clogged passages. Most recently I had to hand turn a real fine drill bit down the accel squirter nozzle on an import carb...found a tiny piece of grit stuck in the nozzle even after repeated carb spray/air; I could tell the spray pattern just wasn't right until I got the gravel spec out.
