howto? Fine Debugging control at cmd line

hi all,

per the docs, i understand i *can* define/change the global pgsql debugging
level at the cmd line by passing, say, pg_ctl the '-o "-d 5"' option,

AND,

that i can finely change loglevel options in postgresql.conf, e.g.:

> client_min_messages = debug5 # debug5, debug4, debug3, debug2, debug1,
> # log, notice, warning, error
> log_min_messages =debug5 # debug5, debug4, debug3, debug2, debug1,
> # info, notice, warning, error, log, fatal,
panic
> log_error_verbosity = verbose # terse, default, verbose
> log_min_error_statement = debug5 # debug5, debug4, debug3, debug2, debug1,

can I, however, *individually* change these "fine" logging controls at the
command line, and simply re-HUP? e.g., for just a quick debug session?

seems like it might be reasonable to do so, but i think i'm missing the
(possibly?) obvious ...

or, does one make the change in the .conf file, and then rehup?

any pointers?

thanx!

richard