Once processes are more or less defined (or redefined) with the participation of staff (meaning that they get to give feedback) you can implement a policy of 'all processes need to follow the documented procedure. Procedure can be changed if needed'. This will in turn help to keep your documentation updated.
In fact it is essential that the processes change over time. Putting in place must-be-followed processes is counter-productive if there is not also a process to vary those processes. You must expect that the processes put in place today will be found deficient in a few weeks or months.
Put another way, one of the most important processes is the "process review" process.