Ilford: "then agitate, as during development, until fixation is complete,"
http://www.ilfordphoto.com/Webfiles/200629163442455.pdf (page 9)
Kodak: "Agitate continuously for the first 30 seconds and at 30-second intervals after that with a hardening fixer"
http://www.kodak.com/global/en/profe...dbwf/edbwf.pdf (page 5)
Agitation similar to developing: Yes. Constant agitation: No.