Custom stamped candles are surprisingly easy. I made this one in about 15 minutes, with supplies I had around the house and a Dollar Store candle.
First, stamp your desired image on the tissue paper with either a solid image or an outline stamp that you can color in. If you use watercolors, try to use very little water, as it will "melt" your tissue paper.
Cut the wax paper to approximately the same height as your candle, but at least twice as wide. Place the image on your candle and wrap the wax paper around it. Hold the wax paper tightly by the "tails" -- "smushing" the image tightly against the candle.
Warm up your heat gun for 30 - 40 seconds and then heat the image, through the wax paper, moving the gun constantly. Times for heating differ, but generally I heat the image until the wax paper starts to look a little "wet".