Better teamworking process or tools than pure Git

We are currently developping an Android game in 2D for a few weeks. Our team is for now composed of 2 developpers and 1 graphic artist.

We are currently sharing the project using Git. The full project is inserted into our repository, and all 3 of us add our work in it and commit.

The graphic artist, however, is not familiar with Git and has regulary trouble using it, with sometimes bad commit we have to revert with violence. It's not his job, so we can understand it. We also know that Git is not really good with such binary files.

With a audio artist in process of joining, not familiar with Git too, we feel our process needs a change sooner than later. While this topic is a bit documented online, we can't find any recent content on this.

Have you any better process to share project using Git ? Or have you any better tool for Unity collaboration ? Any help on this topic will be greatly appreciated.