The trick will be that, because the MSP install is already up and running with existing volunteers, the first time you do the sync you are going to have to make sure that all the volunteers in MSP are properly "matched" with the members in your management software. Its possible that some names in your management system do not match exactly those in MSP, which can lead to some members not getting linked correctly.
To make sure we correctly match all volunteers between both databases, we will use the following steps:
Step 1: Sync only existing volunteers
The first time a sync is performed, choose "Update information for volunteers in MSP Partner database that already exist in MSP only. Then only those volunteers whose name match with a members in the church management system will be updated and linked to their counterparts in MSP.
Step 2: Identify volunteers who were not matched
A spreadsheet can then be generated from MSP' Rosterizer and the External ID field can be included from the list of All Available Fields. Those volunteers who were NOT matched with members in the church management system will not have External IDs - the External ID column in the generated roster will be blank for those volunteers.
Step 3: Update volunteers who were not matched
By filtering for the rows / volunteers having this blank External ID column, name mismatches can be identified and corrected within MSP. Then, go through the synchronization process in step 1 a 2nd time to link the rest of the volunteers.