SmilingWolf, a forum member, has kindly written and donated a very clever script to enable hashcatplus users to sort, filter and convert WPA capture files efficiently.

The script is called Script_it.sh and it runs in Backtrack.

Note that with release of hashcat and hcxtools (https://github.com/ZerBea/hcxtools) there's no more need for cleaning. Please use wlandump-ng to capture all the different kinds of WPA handshakes.