Productivity tool to help me add multiple fields at once
Just wondering about the use case for hundreds of fields - this seems a bit bizarre. Maybe consider using Field Collections to group similar fields and combine with use multiple values per field on a field collection.

As for a possible solution (although not recommended since a lot of things could go wrong) - if you have many similar fields you could export some "base" fields using features and copy-paste inside the features' files the relevant fields. Clearing cache or feature-revert would create the relevant fields.