I think the key is having fresh yeast and sufficient sugars. Making a large starter and immediately pitching and then bottling should work, but with that large of an addition, I would be concerned with the flavor being affected. It may not be a problem, though, and with it being infected, your options are fewer. I would probably opt for a gentle transfer of the fermented beer onto the starter in the bottling bucket, rather than a violent dumping of the starter wort into the fermenter, but that is just me and a concern over oxidation - active yeast should prevent that from being a problem, so YMMV. Good luck!