Drawing salve will treat the scab i.e soften it, but will not treat the infection itself which can lead to the infection continuing to grow under surface when it could be being treated. I have also heard of a vet recommending it, but it was in conjunction with prescribed antibiotics.
Her bumble foot in the pictures above is not severe maybe moderate at the worsr. Are you 100% positive that you're not wrapping her foot too tightly? You don't need to duct tape it, in fact if it comes in contact with any skin it can rip it off, it won't allow the skin to breathe and increases...