You would like to start practice in watercolor and ask yourself what kind of brushes do you need for the watercolor painting? I would say – it depends on the techniques but let’s see on the most universal kind of brushes.
If you would like to paint in the middle/small format, let’s say A5-A4, it’s still useful to have a big soft brush for the large areas. Even if you are painting one flower on A4, you still need a sufficient brush size to fill the whole shape of a petal at once. It’s important because with a small brush it will be too slow and also you risk having particles, stripes and non-uniform fill on your watercolor flower - so with a big and soft natural brush, it will be easier. Personally, I love the squirrel brush Da Vinci N1 or Winsor & Newton N0. I use it already for years!
Middle brush - for the main work. Painting the shadows, add nuances of color, add some details. Normally it's number 4 or 5.
Small brush – like 1 or 0 sizes. For little things - like details on flowers, berries, leaves, and so on. This little brush should have a sharp end. Why is so important? Because it affects the accuracy of your painting. Well, of course, it depends on your style, here I’m speaking more about mine, but the sharp end also gives you much more precision and control. So, my advice – do not spend a lot of money on these brushes, pick up two instead, because even some extra priced brushes always lost their sharp end with time…
Also, you could purchase extra small brushes for example for extra small details. It's not a first-need brush but I love to use it and to have them as well in my collection!
Synthetic? I would say it depends on your style. I know some people who use only synthetic brushes. But what about me – I love to use natural hair brushes. But I still use some synthetic - sometimes for the details and maybe for the dry technics too.
I hope this article was helpful for you, so...