Yeah, you're doing it fine. Although, I seem to personally not be getting a notification within the control panel. I guess I just gotta pop in a flashed card, do the OS update, and then get the driver installed manually - then put my 1060 back in.
BTW, know that you will NEED a flashed card for the prior firmware update. I kinda have to wait a while because I left my spare flashed card in my hometown.
Yeah I just use a stock gt120 for my updates. I was already in high sierra when the update came so was using the stock Mac OS drivers, also for me I had to physically push the "check now" box in the driver manager. Then it just started updating the web driver.