Don is at Darkham.
Go talk to the Voodoo Gentleman. Talk to him until he gives you a robe. Now you just need to get the robe to stink fish.
Unlike normal walkthroughs, in Nice Game Hints you can select just the puzzle you want hints for. Here are listed the puzzles for "Chapter Six - The Festival" in Gibbous - A Cthulhu Adventure. The guide you choose only contains information about that puzzle, reducing possible spoilers for other puzzles.