The violas – and infrequently the 2nd violins – tend to be seen as the “engine room” in the orchestra, providing strong forward movement with repeated notes and rhythms. They work nicely under vocals, but they can also add lush richness for the melody line. Double the amount viola together with the bassoon in their tenor sign up for incredibly sonorous, penetrating tone colour.
Doubling the cello together with the double bass with give your bass line more impact. Fresh fruits, both instruments are capable of greater than just bass lines. Mix some misconception a bit by crossing voices – provide violas the bass line and place the melody from the cellos. Your double bassist will even many thanks for the rare melody.
A string section isn't a keyboard. They will deliver long, sustained notes – and in a supportive harmonic role they can add an exceptional smoothness. Hunt for the shared notes between chords and hold them through around possible. If you wish more rhythm you can use a similar idea, though with repeated notes.
For string chords, you don't always need to gain them from the end up. Provide the chord space by moving the 3rd an octave higher and scoring it for that 1st violins.
Using pizzicato (plucked) strings is a wonderful way to add texture. For lush resonance, score them at a nice dynamic, put together with a legato woodwind or vocal melody. A louder pizzicato dynamic will produce a more aggressively percussive sound.