String bowing is an essential part of the compositional process as is all phrasing and articulation, because it reveals your true musical intentions. .You don't have to be precise about string bowing as players will sort out any issues, but being able to bow competently enough to show the players what you want the music to do is only to the benefit of your work.
Bowing (competently, if not expertly!) can be learnt by study and observation and with that in mind, those of you who want to develop an instinct for it might want to look at the link below. All of the bow strokes for violin, cello and bass are clearly explained and demonstrated by a professor.
Who knows, you might just watch a bow stroke and think..that's what I need for some bars in my latest piece.........