Air bubbles rise to the highest point in a hydraulic system so that's where bleed nipples belong and are usually placed. In Ducati superbikes the bleed nipple is placed at the lowest point in the system (duh) so the only way you can bleed all the air out is for the bubbles to be carried along with the fluid as you bleed, and bleed, and bleed the system. It is possible to bleed the system without using a bleed nipple at the master cylinder, but it takes a lot more work.
So, the Ducati clutch line is notoriously difficult to bleed using just the nipple at the clutch slave cylinder. Evoluzione and Yoyodyne, two aftermarket manufacturers of slave cylinders, encountered customer bleeding problem complaints so begin selling a banjo fitting having a bleed nipple for use at the highest point in the hydraulic system. It works.
However, you don't necessarily need one. You can try just loosening the bolt slightly and bleed with the regular banjo bolt as if it were a bleeder type. Careful though, any sprayed hydraulic fluid will damage painted surfaces.
You could also remove the master cylinder from the handlebar, and position it so the banjo fitting is down and the reservoir is above it.
Darryl Samson posted a clever idea recently. Use a large balloon, inflated and fitted over the top of the reservoir as a pressure bleeding system. Just blow it up and put a tie around it so you can stretch the mouth of it over the top of the reservoir (after filling it) and release the tie.
One workable approach is to have one person pump the clutch lever like hell (then hold it in till the bleed nipple is opened and closed again), another person keeps the clutch master cylinder fluid level full, and a third person opening and closing the slave cylinder bleed nipple while watching for bubbles. Remember the flow has to carry the bubbles down and out. Eventually the pressure builds, lever firms up and the bubbles stop. Go for a ride and then bleed it again to be sure.