Since your goal is to make a batter that is not too thick (you should aim for the consistency of a thick omelette mixture) eyeball the rest of the ingredientsadd a little milk (let's say 1 cup) and mix adding the flour little by little (about one handful). Make sure that the batter is not too thick, if you realise that you have used too much flour, add some more milk. If the batter is too runny, add a little more flour.