Paypal (Labeled as "XCheckout" in Luminate) can be filtered the following way:
  1. Create a transaction report in Report Writer
  2. Select the fields and column headers
  3. Under step 5: Configure Filters select the following:
  4. Payment Method -> Tender type ID -> XCheckout
Save and run your report, and only Paypal donations will show in the results.  You can adjust this report for any payment type.