Vacuum Brake Bleeder?

Just bought a hand pump vacuum brake bleeder. Does anyone use these? System was empty after replacing brake hoses & master cylinder. Bled master cylinder before install. My hand went numb with the manual bleed pump before I got any fluid out. Wound up using my electric vacuum pump. Then it started working.

Got so much foam and bubbles from air leaking around the bleeder screw, couldn’t tell when air was out of system. Is there some technique I don’t know?