What are the best paintbrushes for use with watercolour? 

Watercolour brushes are the best as they have soft bristles, making them ideal for working in smooth layers of colour. The size of the brush is crucial depending on what you want to do; the belly of the brush is the widest part and the bigger the belly, the more water and paint can be carried. Smaller brushes are great for detail, but they don’t hold as much water and pigment.