Glory to Jesus Christ!
I simply say: “Lord Jesus Christ, Son of God, have mercy on me a sinner”
Most people will use a chotki (usually a knotted cord), I have two but I no longer use them much.
Counting seems pointless, unless you want to be reminded to stop.
I have taken to using a ten-bead string of Franciscan penance beads which I will pray along back and forth. I usally will interject a doxology at one end of the beads and a PaterNoster or Nicene Creed or act of Contrition at the other end.
A good book to read might be the “Way of the Pilgrim” a story actually, which will also inform you about Slavic spirituality.
The Early Church Fathers expounded on it a great deal from the Fifth century on. You may wish to read the Philokalia (a collection) as well because later in the East the prayer assumed a much greater role in Eastern Spirituality and many of the leading lights wrote about it.
Archbishop Joseph Raya (a Catholic) wrote about it in The Face of God and Kallistos Ware wrote about it in The Orthodox Way.
God Bless all in their spiritual quests!
In Christ Always,
Michael, that sinner