Indeed, advertising suffers from a severe signal-to-noise problem.
Like the OP, I make a hobby related product as a side hustle. There are some sources of word-of-mouth advertising through web forums for enthusiasts. Usually you have to give something before you can get something back, and respect the forum rules. I never mention my product unless someone specifically asks.
Also, I was an established member of a forum before I ever even dreamt up my product. I made a couple to give away, and another forum member wrote up a review. The rest is history. ;-)
