favorites for interiors, especially with the acrylics, are some 1/4 to 1/2" flats that were bought in Little Tokyo in LA for Japanese calligraphy and ink paintings. And they were cheap, back in the 70's they were 50 cents for the 1/4". But you probably have to be close to an area with a Japanese or Chinese area to find them. Haven't really looked for any brushes in 20 years. The important things are to keep them clean, store them with the bristles straight and in a moth proof container. Had a $25 (1980 price) kolinsky water color brush munched by a moth years ago: almost cried.