You will need to create an export specification for each type of file. You
do this by manually beginning to export a table/query, and when the export
wizard window appears, go through all the steps until you get the last
screen (to do the actual export). On that screen, at lower left, you'll find
an Advanced button. Click that button. You'll get a screen that has all of
your settings displayed. Click the Save As button on that screen and choose
a name for the specification. Then you can cancel the export.

You then can use that specification in the TransferText action as the
SpecificationName argument.