One of the key features of an effective SOP (Standard Operating Procedure) is the ability to capture each step along the way. I worked with a great team yesterday and this was one of the things we discussed after attempting to write some SOPs.
It is clear that writing them in isolation prevents you from getting the most out of your SOPs. Having too narrow a focus on the instruction stops you from writing a well rounded document that anyone can pick up. Working with others can help to prevent this.
Assuming that everyone knows all of the bits in-between the steps you have outlined is a recipe for disaster. In many cases the SOP isn't for you, it is for the new person joining the team, who doesn't know the process or the background to the way your department works. The 'bits in-between' are therefore essential.
Don't worry about the length of the SOP either. Including all of the necessary details rarely bloats the document so that it is unusable. What is unusable is a SOP that is missing the right information.
Take the time required to write your SOPs to ensure that they are complete and useful. By getting someone else involved that isn't directly involved with the process you should be able to write a decent SOP pretty quickly. With a good set of SOPs behind you, you should be able to improve the productivity of your team and protect yourself (to some degree) if one of your team members leaves.
...fixing MRP systems and re-engineering business processes