I don't usually make -all- the fur. I make the highlighted and shadowed furs, then color in the rest with a 'feather' brush so it varies in tones. If you do the areas that are in the light in a very light/bright color in a zigzag pattern, then do the same with a darker shade of the color the fur will be (or if you have Adobe PhotoDeluxe the same color will suffice, if you don't mind closing the pic and reopening to cause the shadow to become background and thus able to color on top of it...)
But, I use APD, not APS (adobe photodeluxe vs adobe photoshop) so it allows me that bit of freedom...