Again, the thing about Dodging is that you have to do it at the LAST possible moment, before Bayo would get hit. That's what will get you Witch Time.
Think about it, as if it were Punch-Out, if it helps. Each enemy, including Bosses, has their own different "quirks" that basically help to tell you when they're trying to kick your ass. Learn these, and then practice dodging those attacks at the last possible interval, and you'll be much better for it. Mashing Dodge won't help you. Because Bayo only gets 3 flips before she'll go into a final one that you can't cancel out of, it's really not worth just spamming it.
Once you get good, then maybe you can try using other Accessories to mix it up a bit. For example, one accessory (my fave), basically allows you to channel your inner Street Fighter Third Strike player, and PARRY DAT [parasitic bomb]. Works on everything except things that would "grab/throw" you!

Another thing you may be interested in, is the Beads. With this, you don't get any more Witch Time opportunities, but instead, you'll produce a "bomb" from a successful dodge, which can do quite a bit of damage in itself. Depending on the type of player you are, this might end up being a better thing for you than WT ever was.
Finally...another note. Put on English subtitles, if you already haven't. You won't understand a lick of what the big bad angels are talking about, unless they changed that in the US version.