Stupidly got a few drops of water down what I think is the inlet pipe when removing my oil filter... Don't ask.

Anyway, I now want to flush the system as I am worried about the water, got a few questions:

1. Is Dexron IID ok? I have Castrol PS fluid and it say ok for Mercan and Dexron IID vehicles

2. Can I just suck out the fluid in the reservoir, or should I take off one of the lines and flush it properly, if so what line do I remove?

3. How much fluid is required?