I love, love, love waterbrushes and the Kurtake Fude Waterbrush is by far my favorite. As you can see from the photo I have a nice stockpile of them. I find the portability of them is a huge plus and carry one of each size in my art travel bag at all times. This particular brand of waterbrush has a nice long barrel, although you can also get them with a shorter barrel also. The longer barrel makes the brush approximately the size of a regular pencil and is my personal go to. They come in 4 sizes, small, medium, large and flat.
One of the main reasons this is my favorite is that it has a filter that helps the flow of water and also helps keep the water from seeping out of the pen. The filter does mean you can't just run water into them from the faucet however if you hold them under the water and give the barrel a squeeze they fill up easily enough.
Some people don't like waterbrushes because the can't figure out how to control the water flow when squeezing the barrel. I will admit I am one of those people. Here is how I work around that. I simply squeeze a bit of the water onto my table, or another piece of paper, and dip the brush tip into that rather than trying to squeeze the proper amount onto my actual art piece. I find this give me much better control especially when I need a dryer brush at times.
These brushes can be found very easily online, I personally get mine on Amazon. You can find them there either individually or in sets. If you have never tried a waterbrush I highly recommend trying these!
Hugs & Love from Ranae'