I use the Certo recipe, but I also bring berries to a boil, remove them from heat, place in food mill to help remove most of the seeds- I hate that seed flavor, then I measure out for the recipe.
I guess you can boil until the natural pectin takes hold, but I am always in the "need" to get it done and over with. You can top with parifin wax (atleast 1 inch thick, make sure no juice comes up with it) and when you want to get it out, push down on one side and pick it out. Us kids always nibbled on the waxed jelly, miricle we lived! lol)
Also, I use quite a bit of Lemon in my black berry (raspberry too) and because I like that tart, I use a whole lemon for 4 cups of berries.
Often when I make blueberry, I'll add 1 tsp lemon and 1 real good teaspoon of Cinnamon before boiling. It gives it a nice rich flavor. Good luck, keep us posted and cant wait to hear which recipe you used for your project! Take care.
ps- not that I want you to do what I said, just love to hear how others do their jams and jellies! I may decide to do something different!