On Thursday morning of Holy Week, we went to the Church of the Holy Sepulchre, which happens to be one of my favorite places in Jerusalem. We went to watch the Greek Patriarch performing the Ceremony of the Washing of the Feet. The Church was crowded with people so we climbed up on the roof to get a better view.
It was a fairly long ceremony because the Greek Patriarch had to have his heavily decorated robe removed; he wore a much simpler white robe for the ceremony. He washed the feet of 12 of his clerics while prayers were recited. I can still hear the sound in my mind. Afterwards, he sprayed the crowd with the leftover water from the ceremony.
We didn't see the Latin Patriarch celebrating the washing of the feet, but it is a much simpler process inside the Church (if the weather is decent, the Greeks do it outside). Afterwards, The Latins go to the traditional site of the Upper Room on Mount Zion.
The Armenians don't do their ceremony in the Church of the Holy Sepulchre at all; they use the Cathedral of St. James in the Armenian Quarter of Jerusalem. The Copts use the Church of St. Anthony in the Coptic Patriarchate. The Coptic Archbishop washes the feet of the entire Coptic congregation.