As someone who experimented with polyphasic sleep for about a month, I actually don't think it's totally necessary to use naps or WBTB for WILDs. It will definitely help, but my one and only WILD was actually done when going to bed normally for the night. That's probably because I trained my body to enter into REM sleep immediately upon falling asleep, and anyone could do that. Of course, I'm not as good at that as I was when I was sleeping polyphasically, but it still helps a lot, I think.