you might want to have a look at my datashift gem (https://github.com/autotelik/datashift)
it provides import/export facilites between Excel and active record and also provides facilities for paperclip attachments
For example given a User model with photo attachment, you can provide a path to the image in a column and the importer will create a paperclip image
and attach to the parent User model
even if it doesn’t exactly fit your needs you should be able to extract code to get you going. plenty of examples in the specs.
hope that helps