Hi Giovanni, I 'm not sure if I understood your question but there is nor right or wrong direction of a pick. For the cloth it doesn't matter weather you start a pick from the left or right side as long as your foot is on the right treadle. It's no problem to throw two picks on after the other starting from the same side with two different shuttles/colors and on two different treadles.
Make sure you watched Ep 5.4.. In "on theloom" you can watch Jane weaving using two shuttles.