IN RB-
enable input monitoring in audio preferences window (ASIO must be selected)
do not enable 'record IM or the reverb will get recorded.

Go to the track, select DX FX button and on the top box scroll to bottom to use InputMonitor with realtime effects..

ASIO must be on for this to be enabled
As Mac mentioned, it does tax the system, although I have used it on an XP machine with 2 gig RAM and Athlon 2.1gHz single core CPU.

I prefer Mac's method in day to day work here.

I do not work here, but the benefits are still awesome
Make your sound your own!