I use this exercise for runs, especially those that contain an unusual number of notes (seven, for example) or that don’t follow a scaler pattern. 

1. Choose your run; don’t make it too long to begin with. Be sure you have fingerings and bowings.
2. Play the arrival note with beautiful tone on the right bow.
3. Add the note before and play the two notes together 5x, getting faster with each repetition.
4. Add the note before (pay attention to bowings) and play the three notes together 5x, again getting faster with each repetition.
5. Continue adding notes in the same manner.

EXAMPLES

Tibor Serly: Rhapsody on Folk Songs Harmonized by Bela Bartok, 1950

Georges Enesco: Concertpiece for Viola and Piano, 1946