The Shifts: Berachot 3a
Number of Shifts: Berachot 3b
Shaving during their shift: Moed Katan 14a
Laundering during their shift: Moed Katan 14a
Reason for the above two lines: Moed Katan 14a
Laundering/Shaving on Thursdays, in honor of Shabbat: Moed Katan 14a
Allowing a Kohen to shave on the Intermediate Days of Holidays if he ended his shift on the holiday: Moed Katan 17b
Considering all Kohanim to be on their shift during the holiday, because he shares in the Showbread and Gifts from the Offerings: Moed Katan 17b
