I agree with Denny. I have done it with a dropper/plastic syringe that they use for children's medication. Use the dropper on a 12-oz glass of beer and check to see how the beer comes out best. Then however many drops you use for the glass, multiple it out for the whole keg (5 gallons is 628 ounces divided by 12 is approximately 52 beers) and then add that much for final packaging (keg, bottling bucket, etc).