I wrote papers in graduate school using a typewriter before switching to a Mac Plus. It was a Smith-Corona and used a cartridge "ribbon" and a special "correction ribbon" that lifted off the text (instead of using white-out).

It wasn't a Selectric, though, so mostly you just used it as a typewriter. Selectrics were expensive and mostly used in business rather than by individuals.

Even the IBM Selectrics were nothing like as good as having a word processor, which is why the transition was so fast. A friend of mine was in commercial real-estate in that period (mid-1980s) and discovered that with a computer, he could type his own offer letters and not have to bother with a secretary. My brother's law firm went through something similar. In a handful of years, there was huge adoption.