How can this be so simple?

If the answer really is just to bath in some NaOH, then there is no reason for a hobbyist to try create corona treatment, or to buy ready-subbed materials more expensive and harder to find.

Well, it makes sense that this has not been described before; in an continuous industrial process, very long chemical soaks are not feasible. But for us and our sheets, it does not matter at all.

Now we only need a test with a real emulsion. Water beading test is the first step, coating gelatin with coloring and testing in water is a better one, but a silver gelatin emulsion may behave differently still. I had a case when I was testing acetate subbing formula that it worked for test coating with gelatin and color, "developed" in solution of sodium carbonate for 10 minutes or so, but it didn't work with real emulsion at all.

I have fingers crossed here that your test with real emulsion works. Good luck!