How do prepare your Soldiers for SGT/SSG Promotion Boards?

I'm in the process of working out an official mock board program for my unit, and I know that another set of eyes on a situation can really increase the effectiveness of the outcome. So far, we have a study guide based on Doctrine 2015 that also explains the board process and what will be expected of the Soldier and the Sponsor. I'd really like to go into more detail about preparation for the board BEYOND just the Q&A.

The other problem I'm up against is getting participation. This month was the first Mock Board of my program, and the only Soldier who showed up was my own who I was sponsoring. He blew the doors down on the actual board, but I couldn't help feeling like I could have/should have done more to reach out to the other soldiers. I sent the study guide out to every Soldier on the MOI, but didn't have sponsor information and never got any replies from the Soldiers themselves even acknowledging that they had the study materials. Admittedly, our unit is not an easy one to keep everyone in the loop as we are part of a government agency and the "company/battalion" is spread all over the world. I really want to bridge this gap.