Here is how I usually do I make render of a shape with a basic volumetric cloud shader. I import the image in photoshop, make a new layer without the background and i start to give the "fur" effect using the "finger" tool (with a 50% pressure) I start from the border and finish in the center of the "character" Then I draw the eyes (or I imort an image with the corresponding mask image) I add some shadow on the fur with a smoth brush.