some notes to simplify the process:
1. Using "msbuild" instead of opening .sln file with visual studio.
2. "msbuild" has a "/t" option to specify the project to be built in a solution, so boringssl can be skipped without modifying the .sln file.
3. Visual Studio has a feature called "property manager" in which you can load the .prop files in git into your own projects. The .prop file contains the necessary information about including directories, lib directories, lib dependencies, etc.
4. Run "cmake -G "Visual Studio 14 2015" -Dprotobuf_BUILD_TESTS=OFF ." in the protobuf/cmake folder will generate a protobuf.sln file including both Debug and Release configuration. (Actually, MinSizeRel and RelWithDebInfo in addition)
hope these information will help.