1) To make obtaining this and all other achievements faster go to options and turn speed play on
2) Custom play -> Classic -> Two players -> select location (no need to change default location)
3) Select human for player 2
4) With player 1 (you) roll dices once and select square with most points.
5) With player 2 roll dices once and select square with “-“ mark or lowest points.
6) Continue until you finish the game and you can start new one right away.
I suggest that you complete adeventure mode first and then classic, rainbow, duplicate and battle modes until you have unlocked Classic master, Rainbow master, Duplicate master and Battle master. Then check your stats for Victories (Extras -> Statistics). You should have around 40 victories. Then if you start with Classic mode, you should unlock Classic sensei at around 130 victories. If you jump from mode to mode, you can't keep track how many victories is needed before achievement unlocks.