This is very simple!
When I started to do the video, I realized it was going to be ridiculously annoying to listen to the buzzing of the heat gun. So, I took some photos instead… well, my (almost) five year old took them for me!
When coloring on the paper, I have the heat gun in one hand and the crayon in the other. I color directly on the paper with the crayon. The heat melts the crayon onto the paper.
When the crayon gets too small to hold and heat, you can melt the piece of a crayon in a bottle cap. You could then drip the crayon onto your page.
Of course the bottle cap will be REALLY hot, so be careful not to hurt yourself!