[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.
It probably goes without saying, that you shouldn’t be handling these nasty chemicals without the right set up and a good idea about safety. You should know the right way to mix water and acid and have appropriate lab gear and safety equipment. [Marko] mentions getting acid from a battery, but these days it can be hard to get to the insides of a car battery. Luckily, it is pretty easy to buy chemicals online and locally — some stuff you don’t want to ship.