I use a Bristle Brush to base in background color and anywhere a heavier application of paint is needed. These brushes perform well and withstand the scrubbing technique often used in background applications. My choice of bristle brushes are the Professional Permalba Brushes
from Martin/F. Weber or the Scharff Bristle
215 Flat series.
The Scharff Classic Series is excellent for detail oil painting of any subject. I use the flats for creating nearly any subjects form and detail with the exception of foliage. For foliage and floral detail I highly recommend the Scharff Classic Series Filberts.
I use the Permalba Red Sable Flat brush when I need a soft touch for doing fine detail in still life paintings, florals, buildings, etc. A Script Liner is used anywhere fine lines or very small detail is needed.