Slow motion is pretty hard. But I managed to get it right in an animation I made called "Pirates Rule!" where I had this guy duck as a cannon ball shot over him. I only animate at 15 FPS, but I think it was still pretty great. You just need to take more pictures and try to make your movements as smooth and slow as possible. I had to build this really weird stick thingy to make sure the cannon ball stayed on the same route, and I put a special henge on it to bring it up for masking. It is really time consuming, but the end effect is absolutely spectacular.