Makeup sponge blending technique. Paint base color (bottom). Then paint one end of a makeup sponge with the other color. Dab at the top of the nail till the colors blend together. Finish and smooth the transition by sealing with a topcoat.
Paint your nails with a base color and let them dry completely. Then come back and paint a layer of another color on top, and before it dries, you dab pieces of wadded up saran wrap on top lightly, then top coat