Not sure about the oily film.

Use NAC with caution and keep a close eye on symptoms (I'm sure you already know this). You could start anytime but if you have headaches, you may want to lower the dose or stop for awhile.

About chlorella...

I am very grateful for Cutler's book. It is a great source of information, in fact, the best I've found.

Despite the wealth of information it provides, I have seen other reliable sources that have convinced me that chlorella may be beneficial for mercury detox, so I do include it in small amounts in my daily protein drink.

It's common to find small disagreements among specialists , especially on a subject matter that is still being explored, so it's up to us to make decisions that make the most sense to us.