Best ways to formant shift a vocal w/o melodyne

So when pitching down vocals for a genre like deep house, the pitch shifter in Pro Tools doesn't seem to be very effective. Is there a better way to do this in pro tools outside of the audios unite pitch shift? I know varispeed is a way that I'm not 100% about yet, just based off not having used it for this a lot. Also melodyne but I don't have it. And another option is Time shift. Just wanting to hear what you think the cleanest ways to do it would be If I'm going as far as an octave or more.