If unable or unwilling to enable package restore, a developer can easily add all packages by command line, as explained in this question:
You can use nuget.exe to restore your packages. Run the following command for each project.
nuget install packages.config
You can also run this in a pre-build command, as explained here:
$(SolutionDir)Tools\nuget install $(ProjectDir)packages.config
But really, package restore is easier, it merely requires a few clicks.