You know I only add it to veg very rarely. I'm an Earthjuice user, and they use it in both the Grow and Bloom formula so it's included the entire time I suppose. If it's already in your regular nutrients I would hold off adding extra until later in the cycle.
I've been making a switch recently however, to enriched soil and utilizing only solutions of liquid bone meal and molasses to increase bud size in flowering. I've been really happy with the results.
With the DWC, as I mentioned I only add a weak solution and then later in flowering. I run organics in the hydro so essentially I'm growing the plants in a weak tea throughout. My issue has always been developing the same fungal rich ecosystem that feed the organic soil, as fungus simply grows poorly in saturated hydroponic mediums.
In organics, fungus is primarily responsible for providing the bloom appropriate nutrients. I experimented with added wood chips to the hydroton to promote fungal growth and had excellant results, but I had to inoculate the chips before hand layering them on rich, moist soil in a bin in the garage for a few weeks. I'm still playing with the amounts and so forth but I'm happy thus far.