Incremental backup using mongodump

My task is migrate mongo DBs ( 10 or more ) from source to destination with less time.

  1. We find the most realistic approach, migrate full mongodump & restore on target.
  2. After restore use mongodump oplog logbackup every 30 mins all databases and restore on destination , I don’t know how to take timestamp and Timestamp(1470923942, 1) how to automate.
  3. It will apply the same until it reaches to the actual downtime for cutover, we want to automate dump & restore in crontab until cutover
  4. How do we guarantee data consistency and integrity while doing this above method.

I don’t know how to handle the incremental backups every 30 mins for more than one database, is there any smart way to sync db entire DB.

Looking for your suggestions and thoughts to meet my requirement.

Thank you in advance .