1. Use a small paintbrush.
2. Dip into some slightly diluted acrylic acrylic artist paint.
3. Quickly begin to splatter the paint onto the board with the flick of your wrist.
This technique can be done with slightly diluted acrylic artist paint. Spray paint can also be used — spray an amount enough to puddle into the cap and dip the paintbrush into that.
And remember: SAFETY FIRST, ALWAYS USE EYE PROTECTION when using spray paint!