[Marko] styles himself as a crazy chemist. His video showing a fast tin plating solution for PCBs (YouTube, see below) doesn’t seem so crazy. We will admit, though, it uses some things that you might have to search for.
The formula calls for stannous chloride — you could probably make this by dissolving tin in hydrochloric acid. There’s also thiourea — the main chemical in silver-cleaning dips like Tarn-X. Sulphuric acid and deionized water round out the recipe.