I've had very good luck dumping the warm/hot gelatin mixture on top of cold beer (even carbed) and then letting it sit for a couple of days. Pour off a pint or two and it's noticeably clearer after that.
One of the things that gelatin will help clear is chill haze. But if it isn't formed the gelatin can't do anything about it, ergo, the beer should be cold first. Also chilling alone will help more stuff precipitate from the beer so the two will work together.