I agree with James .... everyone I have talked to uses different amounts. My Dr. started me at 0.1 units ... that was way too much. Settled in at 0.035 units (boy is that hard to read on the syringe ... really tests the bifocals!). Trimix at 30/1/10 (Papav/Phen/Alp).
I use 31 gauge, 5/16 inch needle ... its not quite as intimidating ... and hurts very litle.
Bob