While there are a number of very qualified and capable developers of manuals it is always (personal opinion) better to develop your processes in-house. The reason being, you have an opportunity to involve your personnel in the development of processes that actually reflect how you run your operation.
This is not to say that attending seminars presented by NBAA and other wouldn’t be helpful as a first step. The NBAA has done an excellent job of developing and amassing standards, however, what and how you use them is up to you. If you are truly seeking an industry standard I would suggest you invest the time in seeking IS-BA0 certification (an ERP is part of their process).
Everyone, large department or small, face the same problem….time and man power, however, once you embark and especially upon completion you will realize that the process has made you into a very professional flight department. Again I stress that IS-BAO is achievable by a single pilot / plane operation or the large Fortune 500 departments, the standards are the same, only the application varies.
At the core of all endeavors (corporate manual and procedures development) should be a Safety Management System, which will become more and more a requirement in the future. The key feature to SMS is Risk Management (analysis and profiling). We have all been taught risks assessment since our first flight lesson, however, the documentation, tracking and implementation haven’t always been part of our departmental processes.
Sorry for the ramblings…and I don’t mean to impugn the capabilities of the myriad of professional services, however, I am strong believer that in-house development better reflects how the department really works…go to the schools, (use a consultant to guide you if necessary…this will sound self serving because that’s what I do) but do it in-house.