I always use left hand because I consider myself a Nyingmapa
I think Sakyapa has its own tradition about mala holding but HH didn't tell students about that details; i mean general students like us....
Gongpodesum means three families lords, Manjusri, Avalokesvara, Vajrapani
There is indeed a tradition in Sakya of holding the mala with the right hand and telling the beads with the left. This is in tri instructions written by Sakyapa Zuchen Tsultrim Rinchen, which were based entirely on the tantras such as Vajrapanjara.
However it is clearly not always observed and not something to worry about.
ps its gonpo desum (mgon po sde gsum)