Clearing the flash channel of rust, dirt or whatever on a P1853 Enfield

This is a P1853 three band Enfield that I got at IMA (International Military Antiques) that has lain in an abandoned armory in Nepal for well over 100 years. After all that time, the passage from the nipple to the back of the barrel is always clogged with rust, dirt, bugs, who knows what. I couldn't even blow any air through it with my compressor. This has worked every time, the first time!