Start by adding 1/4 cup of water as listed in the recipe, and you can then add a little more if you want a thinner consistency. If adding in hemp seeds you will need to add in little extra water too.
Note: I keep avocados in the freezer in small air tight baggies already peeled and chopped. This is such a great way to save ripe avocados for use later. I simply defrost the frozen avocado by putting the bag into a bowl of hot water.