If it was a QB tutorial, sometimes you have to look in the tutorial archive section. It might have be in someone's post and unless they respond I don't think you can ind it.
I believe it was Crayola crayons and then you ironed the back of the block to set the colour but you had to cover your ironing surface with paper to absorb the wax? There is another tutorial on QB using fabric pens or pencils in the tutorial section.