I just went thorough this and have saved almost all of these I have ever encountered over the years. I always start with a through cleaning, then I use a right angle pick and start from the inside and work out thread by thread using pressure to clean and straighten the threads as best I can, next I take a spare correct BB cup and cut rethreading slots in it with a small Dremell cutoff wheel to make a chaser. Then carefully by hand if possible run the chaser in using tools and force only as necessary. Success rate is near 100% over the years as a fomoco and ASE Sr Master technician, at the dragstrip, in the driveway and on the side of the road, requires patience, the right tools, steady hand and now days close up glasses.