The watermelon juice is really easy to make; I usually make it ahead of time so that I don’t have to worry about having a blender out while making the margaritas (I do them shaken, not blended). Cube up or scoop out about 6 cups of watermelon meat, place it in the blender (high speed), and blend for 1-2 minutes or until it is puree. This will produce about 4 cups of juice which will be enough for four drinks. I strain it into a mason jar, the straining isn’t totally necessary, but I do it just to remove excess froth and check for any remaining large chunks.