Niacin, how to use it?

I'm posting this on the Iodine board because I've seen niacin mentioned frequently as a co-factor that helps Iodine do its job better, and also because I've seen other topics on niacin here.

Anyway, I'm trying niacin. 400mg twice a day. The flushing kind.

Now, I hear supposedly the flushing kind, besides being the most useful, is also the most safe. As in, it won't damage your liver. Is that true? There's contradictory info on this. Everyone agrees at least that the time-release variety is dangerous, but some say the flushing variety of niacin can also be if you take too much too long. Others say it's fine to take as many as 5 grams a day.

Also, I'd heard about how activated charcoal supposedly helps mop up whatever niacin knocks loose when it burns fat. If that's the case, when should I take it? A half hour after taking niacin (if I take niacin separate from all other supplements)? An hour after taking it?