I couldn't bear to pre-study, hated it. But I was quite a regular fill-in Watchtower and book study conductor or reader: so, typically, I was up there having not much idea what was in the article / book, but I'd heard it all before so could usually guess the gist.
But I soon realised it didn't matter a damn whether the conductor knew if the answers were right or not, or even what the subject was. I just had to be nice to them all from the platform, utter some clichés, and get about three answers per paragraph, but avoid numpties who'd could be predicted to say something I'd be expected to recognise as wrong (but probably wouldn't coz I wasn't really listening).
Everything just seemed to take care of itself. I quite liked conducting / reading the studies since it relieved the boredom of sitting though one.
The only thing was that it was embarrassing not to have a marked Watchtower. Sometimes I didn't care, sometimes I did something cursory. Toward the end I just ran random highlighter pen over the page for appearances sake.