My friend and colleague Steve Trautman is one of the world’s leading knowledge transfer experts (he was a huge help for us while I was at Electronic Arts) and he has just published a blog post providing some great advice for leaders working on knowledge transfer projects. 
Most knowledge transfer projects fail because leaders do not know how to engage people in either (a) identifying their knowledge (b) helping them create time, or feel supported, to share their expertise, or (c) create time and tools for the knowledge transfer recipients. They sort of wave their hands and hope that people will magically share their knowledge. 
Whether your organization is rapidly losing workers to retirement, poaching, or growing and therefore needing to add people quickly, knowledge transfer is critical to an organization’s success. It needs to be a structured activity that clearly takes the knowledge in people’s heads and organizes it into something that can be both taught but also assessed. Adults learn through doing, so properly structured activities emphasize task “blocks” that can be observed and definitely no greater than 30 minutes in length.  Interestingly, neuroscience is clearly showing that people’s brains reach the saturation point about the 15 minute mark,  so they’re recommending some sort of reflection exercise to help lock in the learning. 
What parts of your organization’s “secret sauce” could be more widely shared within your team? Are you vulnerable to a death / retirement / quit? I’d love to help you figure this out as it has huge top and bottom line benefits to an organization, not to mention retention and capability boosts.