A quick opalescent brush to make things more colorful & shiny!
It's one brush, but it can be used multiple ways. Let me show you!
The brush looks like this when dragged across hard:

Hard pressure is great for some jagged, sharp effects, like hard light & divide.

You can turn on "Blend Brush Tip With Darken" for an even more jagged look.
Gently pulling the brush across the canvas and building up layers gives you a smooth, blended look:

You can also use a blur/blend tool or filter to achieve this, but I like being able to control the brush.
Lastly, there's the option of turning the spray on:

Nice, cloudy fun.