This background is all painted with a brush. You just need to download a set of multifunctional brushes and load them into PS, which can be easily completed. However, it can be done without a brush. It's just a little troublesome. I don't need to say more about the color block in the background. Just pay attention to the color level when spraying with the spray gun. As for small particles, you can use the grid (inside the filter), or you can set a brush (custom brush) and brush it out. Where the background has a gradient, you can use a brush with its own gradient, or feather, or use an eraser to reduce the flow (pay attention to the layering).