I mean, if your prof wants you to mark the heck out of something so that you can be asked to defend your decisions and be graded accordingly, then do as you are told, but I've been in a lot of rehearsals where the conductor will lean over to the concert master and ask what decision they came to about measure 25, because there was discussion of changing what was marked, or it was a fairly bare score where things were left up to the players' experience. Try watching some good groups playing pieces you are familiar with on youtube and air-bowing along with the string sections. See if it feels intuitive. If you know where the music is going next, then where to turn your arm around should feel fairly natural, particularly once you see them all doing it. And then go back and look at scores again and see if where things are marked makes sense with that in mind. You'll notice that when the bow just goes up down up down in a fairly mechanical section, it's usually not marked, because the pattern is obvious. But when the line is expressive, it may be, to help the performer interpret the character the composer wants. In addition to studying crisp, new scores, you might want to borrow on that's been written all over by generations of violin students at your school and see what they've added as notes to self that the composer/publisher didn't put in there to start with.