I figured I'd make a post about how I learned the fretboard in case anyone was interested. It's a lot easier than you think -- but still work. I'm not going to get into the benefits of knowing the fretboard, to each their own. Aside from just brute-forcing, I found I relied on two methods that made it a lot easier and reinforced each other, one involves learning a scale throughout the fret, the other involves learning the notes in the chords of a G Major scale. One technique that helps A LOT is that you can practice without the banjo in hand. Before you go to sleep, on your commute, whatever, you can visualize the fretboard and start running through the following exercises. I promise it helps. The next time you pick up your banjo things will work more fluidly.
G-A-B-D-E-G