Hi Canopy,
This type of work is very complicated like TWrestler mentioned. However if you are good with drafting and geometry then it is achievable. I have not seen Will's article but I am sure it is very informative and will get you on your way. By the way, I was taught this type of work over two years and needed every minute of it. The less difficult way is to represent all pieces with a centerline and draft accordingly to find your angles. These angles can be set with a bevel off of your drawing and then transferred to the sticks during lay-out.
My advice to you would be to read Will's article thoroughly and then proceed with your model. I think you are wise in building the model first.
When you add an overhang with different pitches you have just increased the complications even more so!
Nice!
Build the roof first in your mind and then bring the rest of the frame up to it (plates and everything below).
You will have some cool joinery at your kingposts. You might want to look into having the hips housed onto your kingpost and then have your common rafter on the short wall housed into both hips. Sorry, it is hard not to make all of this sound convoluted.
I was looking through my old pictures and found these two. This might give you a better idea of the joinery (although not completely the same as described above). Most likely the top of your kingpost is going to be "backed" with the roof plane on three sides.