I'm no master at this and just learning myself, but as far as i know the only way to do this is with fuel in the bowls from outside the carbs. I made a float guage out of a piece of clear plastic tubing. I set the carbs on a vise (level in all directions), spplied fuel to them with a long piece of hose running from the fuel tank sitting above the carbs on a shelf. According to my Kawasaki manual the float level should be between 1 and 3.5mm from the carburetor bottom of the carb body when set properly. Took me several tries and it is kinda a pain, but i finally got it. I do belive there are some posts on this subject in here somewhere and also a diagram of a float guage.
