I'd be a bit careful doing that. Just a couple lbs of air pressure is enough. More than that can cause other problems, although I have used that method to take big dents out of tanks.
I've also seen floats collapse, so, If I'm going to put lots of pressure in the tank, I pull the sender and put a sealed converted sender plate in it's place before pressurizing the (empty) tank. When I had a repair shop, one of my guys pressurized a tank trying to get fuel to come out and managed to blow a half dollar sized hole in the bottom of the tank. It turns out the tank had a rust hole that had been repaired with a patch. The extra pressure was more than that patch could take. Not a common problem, but, something similar could easily happen on on old tank. Suddenly having an inch and half hole in a tank with 15+ gallons of gasoline inside is not something you want to happen in your garage!
What a mess that was!