Reading attachments via orchestration is like reading any other record type via orchestration. You would first do a GetItems with the SECTION:FILEATTACHMENTS option. That gets you the AttachmentID(s). Then do a GetFileAttachments using the retrieved AttachmentIDs. Whether you call it easy or not depends on your level of experience with orchestrations.
Thats pretty much where I got to, I guess its then I need to count them, write them to disk quickly and somehow loop round and then recode the email webservice to add multiple attachments, or to take a multidimensioned list as an input ....
I think thats the harder bit or where I'll have to do some serious work myself!!