You must stir it somewhat slowly, if you are using an electric mixer that rotates fast it will produce green crap by my experience.
Also, I strongly recommend getting a fourth bag, a 160 micron. This is critical, I wouldn't even try making ice hash without a 160 micron bag. It's far more important than the 73 micron bag since it collects all the green crap you don't want in your hash. They shouldn't be selling 3 bag kits without a 160 micron bag.