I don't have the table or the postscript command with me,
but I believe postscript will recognize characters in the ascii
table. Also, you can make some characters the hard way
of overtyping a space i.e., a + tilde, using the moveto
(postscript) command. I don't know offhand any trick to
typing Greek word in postscript. Maybe ask folks in the
postscript forum/mailing group.