By painting in this negative space first, you reveal the intended positive space, without actually painting it. There is no right or wrong way to paint here, it is just two different ways of achieving the same goal. So don’t let the words positive and negative fool you into thinking that one is bad and one is good.
Like I said in the beginning, it is not that easy to explain. This is why I have included a variety of lessons and examples below that I found online. I have included videos, articles and step by step demonstrations that will hopefully make this concept a bit easier to understand and to put into practice in your own artwork.