There are RMs to do holy and fire magic, along with a chance to start with a full ATB but you might not have those. Alternatively you can also RW a powerchain effect or use a haste RM which are much more common. The holy attack to force painting out of goddess mode can be physical but the holy/fire on the demon needs to be magic. If you have a knight just give them like Dia or something and have them sling it once at the demon form.