I understand that cracking the captured WPA/WPA2 handshake would take a very long time using brute-force, but I was wondering: what if I have more then one successful handshake? Can it improve the brute-force method? If it can does anyone know a tool which actually does it?
NO! No matter how many handshakes you capure, you still have to brute-force using the dictionary and decrypt the matched packet which is present in all the handshakes, and there is nothing like capturing thousands of handshakes will help you to remove unlikely passwords! So, it will not improve the brute-force method.