How to use C++ Plugin in Project?

So I have a C++ codebase that I would like to use in a project. It has BP-exposed elements which can be used without a problem, however I cannot get a project to compile when trying to use the Plugin’s classes in C++.

I get a wide range of problems, from it not being able to open the .generated include files from the plugin, to includepath problems, etc…

Is this generally not possible? If so please advise. Adding includepath via the Plugin´s build.cs - PrivateIncludePaths.AddRange - does work for the plugin itself, but does not allow for the files to be included from the project that uses the plugin.