I use 4 cups distilled water and 3 tablespoons of coffee. I do the stovetop boil method Dr. Wilson recommends on his site. When I started out, I used my coffeemaker and did equal amounts of water and coffee. The stovetop method makes it stronger.
In doing the enema, I only use about 1 cup of coffee per enema, but I do the back-to-back he recommends so it's another cup for the second one. Doing 2 back-to-back is much more effective than just 1, in my experience.
What's I found easiest is I double the amount of water and coffee and put it in pint sized jars and refrigerate. It's just a matter of filling the sink with hot water and letting the jar sit in it until it's warm. This way I only have to make coffee every other day.