One last question before I go do this.
Yesterday I racked into a spare carboy to help settle and the beer is now cold and ready to go into a keg where I will add gelatin. I'm unclear how to mix well without oxygenating so if I filled the keg 1/2 way and then poured the 3/4 cup of gelatin into the keg and finished filling, would the siphon action be enough to mix the gelatin throughout? Or does it have to go on the top for some reason? Yes, I see that this is really two questions.
I don't think you need to worry about mixing the gelatin. My understanding is that you want to dump it into the full carboy and let it settle.
Due to the positive/negative charged ions (or whatever the science is) it clarifies the beer as it settles through it.
Clarifying a dry hopped beer, AFAIK, is likely to reduce the effectiveness of the dry hopping.
You can clarify in the serving keg. Some people cut a dip tube short for this, some blast out the gunk in the first pint or two. YMMV. I haven't used gelatin in years, but I recall some lumpy gelatin clumps getting into a few bottles. No big deal unless you're not careful on the pour.
Time and cold will clarify your beer pretty damn well if you're not in a hurry.