I have used fix-a-flat before and it worked great! You still need to carry an air compressor since the can of fix-a-flat might only be able to inflate your tires to about 15 psi. In some cases, all you need is the air compressor since the tire will still hold pressure with a nail. The pressure usually drops from around 32 psi to 20 psi with a nail. Even if the pressure drops to less than 10 psi, the air compressor is enough to inflate your tire to 20-25 psi which is enough to get to a tire repair shop. You could carry a flat tire repair kit and plug the tire yourself if really needed.
