You must pair the Bluetooth printer to the Android device first before TracerPlus will see it. TracerPlus has no facility to establish the pairing itself, that is done through the Android operating system.
Once you have your Bluetooth printer paired, you can pair any additional printers you want to use. The Bluetooth connections to the printers are made on demand, i.e., only when a print operation is taking place. That being said, if you had two buttons on your form, both pointing to two print reports (with their own respective printers), on press of those buttons they would find the correct printer and assuming the printer was previously paired and is in connection range, they will send the data to the appropriate printer.