I made a post in this forum probably a year ago or so with screenshots on how to do it in both izotope rx and audacity. The gist is you find the section which has offending frequencies, find what those are, find the harmonic siblings (e.g. feedback at 500hz? check 1k, 2k, 4k, etc for lesser reproductions) and then do a notched EQ filter for just those frequencies for just that time period. Knock off say 15db or so and while you'll still hear feedback, if it's just a 1 or 2 second blast, the listening shouldn't hear distortion where you did the EQ.
and yes, this works, I've done it before. I have to really want to salvage something, but it's very doable.