The influencing process is pull not push. Most communication initiatives are created as a broadcast, as a push. If a message is pushed out, most people duck. An engagement strategy has to make use of the pull influencing process to really engage people.
The OPC Process® works because it is a democratic internal communication methodology; a genuine attempt to connect with each individual in your organisation that demonstrates respect for what the listener thinks and what he or she has to say.
Those that need to understand and absorb your key message do most of the work. Not senior management and definitely not external consultants.
Big or small?