I don’t think that you need to become a compositing master before decided to embark on your first feature film shoot, but I would recommend that you take a week or two to learn what you can about the subject through Adobe After Effects.
From making movie titles to creating visual effects, color grading, adding on-screen graphics, removing objects, or keying green screen - having control over software like Adobe After Effects is a skill that’s worth investing in, and it’s something that’ll stay with you forever. And again, the education is free of charge.