If I Knew You Were Coming, I'd Have Baked a Cake
When I launched For Fuck's Cake (www.forfuckscake.com), I started from scratch, and had to experiment with different mediums to figure out what would work best for the lettering. I've used Buttercream Frosting, Royal Icing, Melted Chocolate, and the most time consuming and frustrating of all, sprinkles!
Each letter is piped using royal icing and immediately covered in sprinkles, which I adjust and move into place by hand with a tiny pair of tweezers while cleaning up any stray icing with a paintbrush. If you don't move fast enough, the icing sets and the sprinkles won't stick anymore. If you move too fast, you smush the icing and destroy the letterform.
Melted Chocolate ended up becoming my default method for lettering on the cakes for time efficiency and legibility, but I plan to explore lettering with sprinkles more in the future.
For Fuck's Cake was created and launched while enrolled in @Lauren Hom's Passion to Paid online course.