The best way to find out more is to just sit down and try it for yourself. That's the point of the walkthrough pictures really, is so that some of you would be inspired to just sit down and try it out. Like I said earlier, the walkthrough is just pictures of me doing just that, sitting down and putting theory into practice.

For me, a wonderful resource has been http://medievalarchitecturalgeometry.com/Index.htm
This site deals with the geometries of 2 Medieval English Cathedrals and dabbles a bit with some other buildings also (for example, a few diagrams of the Hagia Sophia can be found)

The best page on this site is this (in my opinion): http://medievalarchitecturalgeometry.com/A3%20The%20Geometry.htm which is a good primer in the methods of Euclidean geometry, although it stops short of telling you how to actually use it to create a building plan or elevation. To do that you really just need to try it out.