Found this on a Boeing webpage...
Aeromagazine
Developing specific processes for multi-engine maintenance.
At those times when multi-engine maintenance may be required during one visit, operators or repair stations should consider the following to help prevent error:
Develop particular checklists that require additional scrutiny.
Require additional functional checks to ensure the integrity of the maintained systems.
Incorporate a nonrevenue flight into the check process after some maintenance actions.
Encourage process thinking by the mechanics. Usually if a mechanic develops a pattern of action associated with an activity, it is less likely that an error will occur. This pattern of action must be correct to prevent errors from becoming incorporated into normal processes (see "Same Process, Same Outcome").
Provide a kit of parts for specific maintenance activities. For instance, if the engine requires an oil filter replacement, all the parts that must be replaced can be included in a kit. Then, if O-rings remain in the kit after the task is complete, it should be obvious to maintenance personnel that the O-rings were not installed.