This is why I never volunteer to beta-read for someone whose work I haven't already read - preferably more than one story! There's a limit to how much improvement one beta can induce in one fic at one time, and I doubt, no matter how hard you work, whether you will want to have your name as beta-reader on the edited results of your striving, if they ever see daylight. Only how do you say, 'Sorry, go back to school, use a dictionary, use spellcheck FGS?' You'd exhaust yourself just entering SPaG corrections, before you tackled word choice, or canon, or common sense, or taste. My sympathies for your predicament! At least badfic doesn't usually see print form, these days.

I can't spell McGonagall (just inserted the second 'l' after checking) without thinking about it, along with apartment and spectacles. So I use MS Word Autocorrect (I am also dead lazy, and typing L when I mean Lucius saves a lot of bother).