I have found it very useful in the past when I managed a small team of Recruiters to which they did their own sourcing to take them directly to client-site and have them understand the dynamic of the lab or space to which they were recruiting so that they understood for example it may be a 1,000,000 line Java code base to which they utilize the Eclipse IDE to which the majority of new employees would be modding this existing code rather than developing from scratch.

This simple example is something that I think that many of us take for granted.  If you are struggling to get your hiring managers the candidates they believe are the perfect fit, I would suggest this remedy if you are local to the client-site.

In cases where you are not local I would suggest a good Skype or Facetime meeting to achieve this or in the case of a highly cleared facility obtain the best information you can share as this goes a long way when you are engaging candidates as you can better tell the story of the environment they will be potentially working in which has always worked wonders for me.