Wind a yard of floss around the fingernails of both index fingers. Use the other fingers to hold in place in the mouth. To reduce floss breakage, use a sawing motion getting floss between tooth surfaces, and use a sawing motion getting out. When in, scrub facing tooth surfaces with an up and down motion or a sawing motion.

There is a Gore-Tex super-slippery floss named Glide that is occasionally useful if food is severely impacted between teeth. However, it breaks easily, so it's not suitable for everyday use.