To get the most out of smart playlists, you really need to have complete tag information. Some of my favorite third-party tools are:
iEatBrainz - This free program examines songs in your library and then creates an auditory fingerprint of the sound of each song to match it with the correct information maintained in the MusicBrainz Database.
Jaikoz - This commercial software (£15 GDP or about $30 US), also uses MusicBrainz as well as Acoustic Ids provided by MusicIP.
Remember that no identification system is 100% accurate so make sure to double check the results no matter which tool you use.