I few years ago I run an implementation project and I used work groups which were established during the project to produce the handbook and procedures. I had 7 work groups i.e. one for ISO section 5,6 and 8, four for section 7. In the groups were present all functions, from top/middle management to employees which were relevant for that section. My moto was "those who are managers also write how to run the operations"
Before production started, a "contract review" was held for all selected people to give the objectives of the work groups, and discussion on the tasks of each group and agreeing on the schedule. Target was to get everybody the same understanding of the output.
For each work group was first given training 1) general about whole ISO standard and terms 2) detailed about their own section.
The work groups were given 1) information on standard requirement, 2) model manual as an example and 3) our existing manual. Their tasks was to review what is our of doing the standard requirement - are theý existing ones or something new or something that exists but not written in manual.
These work groups then produced a proposal on the handbook which was then reviewed and discussed in extended management review meeting with top management representatives and representatives of the work groups.