I have wormed in the water, and this is my theory: it is just like spraying for weeds in your pens. You don't have to worry what the ratio is, as long as the right amount of chemical gets put on the weeds (in your deer).
What I do is estimate the sum of the weights of the deer in a pen, calculate the dosage per the directions, multiply by two, put the paste in a water bottle, fill the bottle half full so there is room to shake it. Then I shake the bottle to disolve the paste and pour it into a container of clean water-what I know will be consumed in about 24 hours. This won't work during a rainy period or if you have standing water, but my deer drank it right up every time I tried it. I normally let the water go dry before returning to filling every day.