Instead of using your fingers I've done this in the past with good results:
1. Put two plastic tubes into the fluid reservoirs
2. Connect them to the bleed nipples on the side of the master (black nipples in top below photo)
2. Bolt master cylinder to booster, connect brake lines to master
3. Fill reservoirs
4. SLOWLY stroke the brake pedal until all the bubbles goes away (helpful to have a spotter here)
5. Bleed the rest of the system working from LR, RR, LF, RF (furthest brake to the nearest)