Back in 1997 when I began my line of modular building card stock drawings I had the same problem you are now facing. How to capture a building for modeling purposes. While my approach may not be the best it certainly worked out well for me.
The following is my combination of tasks.
I begin by photographing the entire structure.
With my wife's help we measure the building horizontally and sketch significant point such as door and window edges, Also any column, or features.
I then go back and measure and photograph each type of window or door or unique feature. for height and structure. A building may have 40 individual windows with only 5 being a unique design and size.
I then measure all the common features such as the brick work. I note the size of an individual brick, and a width of 10 bricks in a row and the height of 4 or 5 rows.
The latter helps me keep the correct scale.
For elevation I count bricks, clapboards or shingles. For stone work I use a measuring pole and photograph it against the building. The following photo shows an 8ft module I created for my trolley layout of a pair of college dorm buildings at Yale University in New Haven CT. In this photo my wife is holding up the pole against the building and I am standing in the street taking the photograph.
We previously measured a collection of individual large, medium and small stone.
In this case I had to measure the building for size but also model the stone work patterns. To accurately measure the height I had to correctly compensate for the vertical distortion of the photographs. The next photo highlight my wife holding up my measuring stick while I dodge traffic to take photos. With this information I was able to fairly accurately measure the height of the building.
I also did several other things. I went to the Yale art/architecture school and library to see if anyone had plans for the building that I could reference. Other sources I tap are the building owners, city planning departments, etc.
Next I try to arrange a visit to the buildings maintenance department to see if I can get a visit and tour of the interior. Seeing how the interior is divided and the interior of the outside walls are created is a great benefit in replicating the outer walls and understand the structure of the building.