Okay, I realize that this is an old post but I haven't been on here in awhile. So........
as for the rennet stirring: I also did a lot of my early cheese making according to the same site the original poster referred to and found that the stir time was WAY too long.
Now I stir the rennet in for exactly 60 seconds, quite vigorously. Then I stop the motion of the milk with my ladle.
As for heating/cooking I'm lazy so I do not use a double boiler. I simply put a very heavy bottomed cheese pot over the burner and moniter closely. I'm not saying this is the proper method but I've found that with a double boiler I always go way over the approximate times given in a recipe.
Now I do use a Ph meter so I guess the timing isn't all that important but I still like to see my makes come out at least close to the recipe I'm using.
I have had a problem with cooking too quickly and it's something that I'm working on. I might have to go back to a double boiler setup to achieve my goals in this area.
My main problem has been with Monterey Jack style cheese. No matter what I do this cheese does not turn out ofr me and I'm certain that it has to do with the cook part of the make.
If anyone has any suggestions I'd love to hear them since I have both red and green jalepenos just wating to go into a cheese.
Okay, that's enough for now. Sometimes I get carried away when it comes to cheese chat.
Dave