automation. lower the level of the breaths pre-processing (clip-gain etc). if the breaths are still disturbing, lower them even more with normal volume-automation. takes probably 5-10mins per song, imho not worth struggling around with an automatic process (expander, de-breather etc). sometimes clearly audible breaths are needed for the dynamic/impact of a vocal-line, no plugin can make this decision for you. similar process for sibilant- and plosive noises.
unless the vocalist have a really bad tecnique, i would not advise him to watch his breaths, because mostly the rest of the performance will suffer.
edit: this thread needs to be movet to the FHO section of the forum