Someone asked me yesterday which brand of brushes I'm using. In general in botanical painting I'm using Raphael 8408 series, #2, #4 and #6. I like them, because they have very very fine tip. Although I have to sincerely admit that sometimes that really long tip is a little bit troublesome. It ends with almost one hair, or two maybe, and sometimes it's difficult to release the paint from the brush, especially when you paint something really tiny.
I wish I could try Winsor&Newton series 7 brushes as I've heared they are excellent. I have to save up for them.
EDIT: I have tried Winsor&Newton series 7 brushes and they are excellent too, although I think Raphaels have a finer tip of the brush.