I used round cotton buds, but toothpicks or pointy cotton buds are as good
You can put a bit of the nail polish in a plate and dip the cotton buds but I was being really lazy and I just dip them straight into the nail polish bottle. And you start making dots!
The same with the other colours
Let it dry and it is finished! Super simple. You can use as many colours and do as many dots as you want. The effect is always fun