Android: How to overlay a bitmap and draw over a bitmap?

I have three questions actually:

1. Is it better to draw an image on a bitmap or create a bitmap as resource and then draw it over a bitmap? Performance wise, which one is better?
2. If I want to draw something transparent over a bitmap, how would I go about doing it?
3. If I want to overlay one transparent bitmap over another, how would I do it?

Sorry for the long list, but in the interest of learning, I would like to explore both the approaches.