I have been voluntarily doing face painting for events with Seward Parks and Recreation, which has given me plenty of practice to work quickly and also work with themes.

Simple pricing: $75 for the first hour + $50 per hour afterwards. On average, I can do 15 face painting designs in one hour, which is approximately $5 per customer during the first hour and $3 per customer afterwards.
Tip/Gratuity appreciated!