you could make it as a premiere? that way people will get a notification of the upload BEFORE the publishing. You could also do the annoying self promotion on your twitter, but I find people going "new video in an hour" tweet to be fairly annoying, so maybe your best bet is to try a premiere. But at the end of the day, even if you promote a video a day before it's released, some of your audience simply might not want to watch it until days or weeks later. So a little tweet notification, setting it as a premiere, or if you have access, a community post, or a youtube/instagram story could work as well.
You don't want to sound spammy and self promotiony though. You might find people will unsubscribe if they're notified TOO early.