Stuck on shingling

 While I haven't been working on this a whole lot, when I have, I've been shingling.  It was straightforward to shingle the rear (left) roof. I haven't decided how I will treat the ridgeline yet.

The front roof (right side of house) was a bit trickier, fitting shingles around the tower, but still fairly straightforward.

The gable roofs, however, are a total PITA and thus I have been procrastinating mightily.

All three roofs have a different slope.  So in order for the rows of shingles to line up visually the way the viewer expects, they have to be laid at different spacing on each roof.  I drew lines on the right slope before I realised this. So I'm having to attach shingles one row at a time, using the spacing on the left as my guideline, and eyeballing the line around the other two sides -supplemented by measurements taken from the bottom of the valley up along the edge of the roof to keep the two sides the same. At the same time, I have to cut partial shingles to fit into the two inner valleys.  It is slowly getting there but not fun.