First take a range of metallic nail colours and a base coat. You could choose from colours like metallic grey, blue, green, purple and jet black. Also, keep a toothpick ready.
Start the process by applying a base coat.
Once it dries, take black nail polish and blot it all over your nails.
Allow it to semi-dry. Apply all the other metallic colours on top of the black polish. You could use a mix of green, blue and purple.
Now, swirl around with a toothpick to create a random pattern. When you are doing the swirling process, you can see that the nails are giving the oil slick look already. Ensure you don’t overdo the swirling process. The various colours should mix well and give a rainbow effect.
Once it dries, add a clear top coat to finish the look!