Editor's comments ...
Not to criticize Mr. Fletcher unduly, but if it is Japanese traditional methods that he is trying to use, then these brushes are unusable.
These brushes have soft and long hair, and they will of course serve to 'paint' pigment onto the block, but that is not the way it is done in the Japanese method. Japanese brushes have quite stiff hair (softened at the tips by rubbing on sharkskin), and are used to 'scrub' the pigment onto the block. By this means the layer of pigment is ensured to be smooth, level, and thin, something difficult to obtain by 'painting'.