-By Jesper Ejsing
I just wanted to tell you about this little trick of mine. It is a neat way of blending wet colours that I use all the time.  I learned it from an animation background painter from back when that stuff was still made in acrylic or gouaches. You’ll need: A badger brush (It is a thick fanned brush that has a round tip instead of a pointed one), and an Airbrush with a large cup, preferable with a lid on it. Fill the reservoir with water. 
The idea is this: with a quick hand you add the 2 colours you want to blend thickly up against each other. With the airbrush you mist the surface with water to keep it from drying while you work on it. with the badger you then let it gently touch the area between the 2 colours, thus mixing them or blurring them together. When needed, you can spray more water and brush in and out of the 2 colors to add shapes or broader fading.
I use this technique primarily for skies and for mixing soft edges in lets say clouds or smoke or mist. The great thing about it is that I can keep semi hard shapes and forms but blend the edges to a soft line. In the end it has more strokes than had I airbrushed the whole thing, but it has less hard strokes than had I done it in brush only. Acrylics is kind of a hard medium in the shape of the strokes, and this little trick allows me to keep areas of a painting smooth and thus lacking focus, creating calmness to the eye and by then adding focus to the areas that are hard and edged. 
On the Ice Giant cover I have added small arrows to show you where I have used the water fusing technique. 
In the 2 magic card illustrations it is clearly visible in the sky.

Well, that was my best kept secret… if you do not count the alien abduction or the crossdressers for the Satan Country Club.