Is there a way to 'Run Custom Tool' for an entire solution?
Why? The custom tool is under development and when changes are made I need to refresh all the items that use it to make sure nothing breaks.
In Visual Studio 2010 there is a button in the icon bar of the solution navigator that will run all of the t4 templates in a solution.
In Visual Studio 2012 show the "Build" toolbar. There is a button in that toolbar that will run all of the t4 templates in a solution.