Like Richard, I also add it directly to my pool, in front of returns. I usually add a half gallon +/- at a time and divide that by three, 1/3 for each return I have. Now Richards experiment with the blue stuff got me thinking (always a dangerous thing) so I will probably start to add 2/3 at the deep end return and the rest at the two returns in the shallow end. To be honest, I don't think it really matters one one or the other. I have read excellent arguments for adding bleach both ways. It shouldn't hurt your filter if you decide to add directly to the skimmer.

Dave