I've removed my rear derailleur so many times that I think I messed up the hanger threading this latest time I reinstalled it. It's very hard to screw in, doesn't even go in straight, and now not even my hanger alignment tool screws in properly. Since my bike is so old, I just bent the hanger to account for the miffed threads and reattached my derailleur the best I could as a temporary fix. Now I want to fix the threads. I've since learned of some methods involving tapping the threads as well as drop-out savers:
How To tap and Clean Threads On Your Derailleur Hanger
How To Fix Derailleur Hanger With Stripped Threads
Based on my description, is it likely that I cross-threaded the hanger? If I need to resort to tapping, how do I determine the proper tool to use? Are there bike-specific tools or will pretty much any tapping tool work so long as the measurements are correct?