Context is everything!

둘 다 써 could be "Both are used" sometime. :)

둘 다 써 1. Write them both (쓰다 : write) 2. Use them both (쓰다 : use) 3. Both are bitter. (쓰다 : bitter) 바로 바로 = 곧바로 immediately, instantly, at once, right away

둘 다 써: use them both 바로 바로: immediately