Check out this blog post on Open String book studies with free viola bow exercises!
Open String Bow Workouts for Viola, Book Two
One great thing to add to the beginning of your viola practice (at any level of playing!) is a short study on open strings.
Open-string studies on the viola can help you focus on your bow and how it interacts with the string. Good bow technique is essential for creating beautiful sound.
This second book of new and exciting bowing workouts for the viola gives you 110 exercises to train your bow on open strings before you begin the rest of your practice.
Since there are no left hand notes, you can focus entirely on improving the dexterity and control of the right (bow) hand. Useful also for students who are struggling with reading notes, this book gives violin a tremendous resource for creating better tone.
The exercises in this book work on on staccato and articulation, dynamics, double stop staccato and string crossing, chords, spiccato, and more! Note: The main focus of this book is on bow control with articulations. Smooth, connected bows and string crossing are covered in Book One.