I have not found help from keyframing Flow / Domain / Density / Temp. Difference. It alwas starts as a small cloud (too big) and then grows. How I can set so it really starts from zero or at least from very tiny poff? I have a quite big curve my smoke flow object.
You could try using long-life particles.
If you use 100 particles, emitted over 100 frames, then the smoke creation rate goes from 1-100% over 100 frames.