After cleaning the glass piece well, keep the design below the glass piece and start tracing the outline using the glass liner. Giving even pressure, press the outliner tube and stretch it to form the required shape.
Allow it to dry well and then start painting using the glass colors. Ensure there are no bubbles and the colour is spread evenly.
You can also decorate it with sequeins, beads or other decorative articles when the paint is wet. For the parts where you dont want the painting to shine- like face, hands, legs- paint it with fabric colours.
Alternatively, you can use m-seal (mix the two pastes provided well in equal quantity to get a clay like finishing and after it dries up, paint it in black) instead of the glass liners.