The Posterize technique described in the previous tip can be used for all sorts of effects. By separating an image into different levels of brightness, we can get creative with brushes. Follow the steps to posterize and make separate layers, then clip new layers to each level and use brushes to paint splashes and splatters on each layer.
You can find an array of brilliant brushes on the Adobe site. To access them, simply go to the Brush Picker (where you choose your brush tip) and click the cog icon, then choose Get More Brushes in the menu.