Use the ^X^W (Write File) and specify PRT:, SER:, or PAR: as the filename.
THis will send the contents of the current buffer to the device. Be sure
and check the filename before using ^X^S (Save File) to make sure that it
still points to the disk filename. You may have to do a ^X^W with the
filename to point it back to disk.
Drop me a line if you have any other questions.