In each project you refer to them (right-click on the project and "Add Link"). After creating your solution or project, Visual Studio should automatically copy the required reference dlls to the /bin for you.
As for multiple copies, since each project is usually autonomous, each of them will have a set of reference DLLs, however, if Project A refers to Project B and you use Project A (for example, Project B is a class library), then for project A there should be only 6 dlls.
- ProjectA/bin/Debug/projectA.dll - ProjectA/bin/Debug/projectB.dll - ProjectA/bin/Debug/shared1.dll - ProjectA/bin/Debug/shared2.dll - ProjectA/bin/Debug/shared3.dll - ProjectA/bin/Debug/shared4.dll
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