You could loop on a repeating section, but remember that workflow are associated to a sharepoint list item, so in that case you 'd loop and create 1 item on another list, where you will have the workflow for those items
How do you actually "find" the data that is contained in the repeating fields? Since they dont actually go into the list item metadata fields, I can't find where you actually reference the repeating data.
You can connect the entire repeating section to a plain text multiple lines of text column in the list (NOTE: it must be plain text). Then upon submission it will store the xml definition of the repeating section data in that column. You can then use a Query XML action in WF to retrieve the data and put the items together and process them however you choose. You can create multiple Collection variables that contain the data for each field in your repeating section on the form, use a for-each loop and Collection actions to put each individual repeated item and then process it however you might want. The X-Path to get a collection of the column values looks like this /RepeaterData/Items/Item/<column name from the form>.