We get a case or two or three of cranberries most years real cheap from a friend whose brother works on a cranberry farm down on the cape. We make about 25-45 gallons a year of sweet cranberry mead and give away a lot of bottles of usually the two year old mead at the holidays.
Anyway, for mead we pulse the cranberries and put them in a mesh bag and add hot water and the honey then let cool to pitching temperature. We let the cranberries stay in there during all of primary. Obviously this exact method wouldn't work for beer but the basic idea of using a mesh bag to make a tea might work, and its not messy. I would think for beer you could make the tea, reduce it, then add pectic enzyme after it cools and add at what point you feel would work best: secondary, primary after krausen etc. If you don't want to boil it you could just keep in mind the volume of cranberry tea you will be adding later on when doing your calculations.
Actually now that I think of it you could drop the bag of macerated cranberries in the wort either for the last 10 minutes (add pectic enzme later) or take some hot wort out near the end of boil and make a tea with that on the side.
Long story short, macerating the cranberries and using a bag to steep in hot liquid works great and is easy. Phew!