It's probably not a very good focus screen changing it for a new screen would probably make a big differance often just over a stop faster. Then adding a fresnel in your case to the rear of the screen could add another 2 stops brightness.

I changed the screen then added a fresnel to my 1961 Pacemaker Graphic and that added close to 3 stops overall brightness compared to the original focus screen, I did measured tests as well as comparative (alongside a second camera). I've a similar screen & fresnel in my Super Graphic and can use both handheld with ease with the original focus hoods.