The best way to properly clean your meat injector needles is to start with hot, soapy water. It does not need to be boiling. If you have used a thicker sauce, and especially one with herbs in it, you will need to spend a bit more time cleaning the meat injector. Instead of simply filling the injector with hot, soapy water, disassemble the entire mechanism. Then, use a bottle brush to gently clean all crevices. Most meat injectors will come with a cleaner, so be sure to use it. If need be, replacement brushes can be found in most kitchen stores.