I'm not sure how you would repair a ripped quilt block. I think you would need to place a small piece of fabric inside the quilt block so that it lays under the rip. Smooth everything out as best you can, sprinkle on the powder, cover it with a non-stick sheet and then press with your iron.
Perhaps Stitchfancy could let you know where she saw the video, or maybe there is one on youtube.