I have done a couple where the master was not bench bled first. Usually the
Vacula will handle it, but you need an air compressor. There are probably less expensive versions of the same thing. Before I found that I got a spare cap that fit the clutch reservoir and drilled a hole in the center of the cap, maybe 1/4" or less. Filled the reservoir, installed the cap, and with the air pressure regulated down to 10-15 psi MAX put a rubber tipped air
blow gun and pushed it tightly into the hole in the cap. Have someone crack the bleeder while you watch the reservoir MAKING SURE TO NOT DRAIN THE RESERVOIR OF FLUID AND RE-INTRODUCE AIR INTO THE SYSTEM. Bleed until all air is removed, probably have to re-fill the clutch reservoir more than once.
If you're a one man operation you could thread a 1/4" npt air hose quick connect into the cap and attach your air hose to hold it in place. There are also brake pressure bleeders that incorporate a spare reservoir to draw fluid from so the reservoir doesn't run out. This was just a simple cheap fix that worked for me. Watch the air pressure, doesn't need to be above 20 psi max so as to not possibly damage anything.