Ok I've found this article recently:

http://www.texasholdem-poker.com/nolimit_betting.php

It seems though the mathematics are wrong.

From what I figure, it is more than enough to put in a pot-sized bet if somebody else is on a flush draw (if he misses I can still bet on the river again)

Say the pot is $100. I bet $100 so the ratio pot vs the bet for him is 2:1 right?
But the odds of him catching the right card is only 5:1 (on the turn)?

So even half-the-pot bet is sufficient here?