In this video I go over different methods to clean your stencils from the softest to the toughest method. It is in 2 parts.
For the cloth I am using in the video, here is the direct link to the travel pack. The clothes are good for anything you want to clean without having chemicals involved (you just need water). If you want to buy them JUST for cleaning the stencils, I think it is not worth it but if you want to use it for cleaning everything then yes this is a good investment.