I find it easier to stir into the liquid before I heat it up. Add some to the water (or beer) and let it bloom, then stir and heat. When I add it to hot liquid it clumps up and takes a lot of stirring.
Then while still hot add it to cool beer.
I’ll usually mix it into some room temp water and let it sit for 15-20 min, then heat it up to 170-180ish in the microwave and dump it in while still hot. Just do yourself a favor and don’t smell it before you put it in your beer… Now that I’ve said that, you won’t be able to help yourself and will smell it, so don’t be shocked with how bad it smells. 
More gelatine info. This is from braukaiser.com from the How pH Affects Brewing article:
[quote]Collagen is a very effective clarifier which is used after fermentation is complete. It is the effective compound in isinglass and gelatin. Collagen is a protein that, depending on its origin and processing has an isoelectic point of ~5.5 (isinglass) [Alton], 7.0 – 9.0 (type A gelatin) or 4.7-5.4 (type B gelatin) [GMIA]. Isinglass is produced from the swim bladder of tropical fish; gelatin on the other hand is either made from pig skin and feet (type A) or bovine (cow) parts (type B).
[/quote]
So it seems Type A is not kosher if that matters to you or any of your friends/family (Type B may not be kosher either but I don’t know).
Then a bit later:
[quote]Because of its wide availability, almost every grocery store carries it, most brewers use Knox unflavored gelatin if they need to clarify a beer. Knox gelatin is made from pork and therefore type A [Kraftfoods].
[/quote]
I do it the way Noonan describes in Brewing Lager Beer (or at least I started there, I may have diverged a bit). IIRC, it’s 1/8 tsp per gallon beer (I use a heaping 1/2 tsp), ~3/4 cup water at ~170* F, add to cold beer and add it before the temp of the gelatine mixture drops below 120* F, mix well.
Wait.
Profit.
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.
What has been everyone’s experience with using gelatin in beers with haze due to dry hop?
Can you gelatin in seving kegs or do you need to rack it off to another keg after using the gelatin?
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.
I’ve added it to the serving keg after it was carbonated and still served it.
Just remember to have a pitcher or an extra glass ready when you pour for the first time. You might get a bit of schmutz in the glass but every pour after that should be crystal clear.
OK. Thanks. And yeah, I expect a little ‘gunk’ the first few pints.