There are a few different ways to silver solder a flash hider. The easiest way is to use a torch, flux, and silver solder. First, make sure the barrel is clean and free of any oils or debris. Apply flux to the flash hider and the barrel and heat up the area with the torch. Once it’s hot enough, apply the silver solder and let it cool down. If you’re not comfortable using a torch, you can also use a propane furnace or an electric furnace. Just be sure to follow the manufacturer’s instructions carefully. Thanks for asking!