You need a warm surface so the crayons will melt. I used a griddle which I completely covered with foil to prevent the wax crayon from touching the actual surface of the griddle to preserve its ability to make pancakes for breakfast!! You do not need a lot of heat so 200 - 225F is hot enough. Place a sheet of white cardstock on the foiled surface and let it heat up a bit. Now, start colouring on your cardstock with wax crayons - they will melt as you rub them on the cardstock!! Just keep adding colour until you are happy with how it looks!! I sometimes use clear wax or a white/light coloured crayon to help blend the colours. I use a small plastic fork to hold my cardstock steady as I apply wax to the surface and sometimes use the tines to move the wax around and create swirly patterns in it. Needless to say, eventually the plastic tines become deformed by the heat and a new fork is in order!! I have removed the paper casings from my wax crayons to help the process go faster. I am using just scraps of wax crayons - the kind that end up in the bottom of the crayon bucket because they are broken into little pieces!! Ask any mother, and she will gladly donate you the broken crayons her children no longer use!!
Once cooled, I cut the papers down to size for backgrounds on my cards. I made them just slightly smaller than the transparencies so that they would not transfer colour to the envelope!! The images are from Dover, printed onto transparencies, trimmed & layered over the wax crayon backgrounds and attached to the front of the cards using brads!!
Just the punch of colour I was looking for!!