Using Butter London's British Racing Green and OPI's Bling Dynasty I recreated one of the most popular manicures of late, The Ruffian, with one of the most popular color combinations, green and gold. Who could resist this?
It's very easy to get the smooth edges of the gold if you have the right tool--hole punch reinforcement stickers (cut in half).
Paint on your base color and wait until it's dry, but not just dry to the touch, dry all the way through. Cut one of the stickers in half and place it on your nail where you don't want the new color to be. Apply the second color and wait about 10 seconds for the polish to settle. Then, pull away the sticker in the direction towards the new color to prevent strings of polish that may form from crossing the color border. Boom, you're done (after you apply a top coat, of course).