How long is long? I have tiny hands and my thumbnails go at least 1/4in past the ends of the fingertips and I've figured out riffle-shuffling. I grip the deck about 1/3 of the way down and only riffle the very top corners, though, so that when they're shuffled together the cards make a ^ shape. Then I (gently) slide them together. If you have really long artful acrylics, though, that still might not solve your problem.