What would you recommend as minimum time for agitation to guarantee uniform fixing with a two bath approach?
2x 1 minute will do it for most papers (Ilford, Agfa). Some papers need more (Kodak). You need to test. Some practitioners go down to 2x 45 seconds, but it also depends on how you count time. My 1 minute fixing time includes a 15s drop-off above the tray before the print is moved to the next bath. Constant agitation during fixing is important in any case.