I'd done something similar some years ago using a different app but the swirling cloud was a darker, purple color. This made for some issues with a mottled light/dark background. What I ended up doing was creating a couple of masks, one being a basic transparency mask and the other being a dot pattern. I first applied the pattern, then used the transparency mask. The result was a cloud surrounded by semi-transparent dots that were to small to easily make out. The result for this particular animation was that the lighter dots worked well over the dark areas and the darker dots working well over the the light areas. I also added something that was appropriate for my project, which was a pair of white gloved hands that faded in very close together, then spread apart to reveal the cloud as they faded out.
As seen in your animation, the higher contrast cloud can make things visually compelling, as does the detail of the image.