Well you asked, so here it is, Bangles guide to making brindles in Photoshop.
I am not great at writing these things, so hopefully it will help you and not be too confusing. This assumes that you do know a little about Photoshop as well, like using layers.
How I make Brindles in Adobe Photoshop 5.0
1. Choose your outline, I will use my Greyhound because they are usyally the dogs I make brindle.
As you can see, all my outlines have at least 2 layers, the front one has the outline, the bottom one is where you put the colour.
2. Add a transparent layer. Use Layer/New/Layer, then accept the settings that come up.
Put the new layer between the two you have
3. Flood the Second layer (Layer 3) with a light colour, I am using tan
Then click the top layer and select all the inside of the dogs, leaving out the nose, eyes and paw pads, with the magic wand
4. Now click the second layer, what you selected on the top layer will stay selected. Make your dark colour be in the foreground.
Then choose Filter/Sketch/Graphic Pen, an options window will come up
Mess with the stroke length, Light to dark and orentation till you get something you like.
Then you should have something like this
5. With the same selected on the second layer choose Filer/Blur/Blur. I do it twice but you can do it as much as you like.
This will blur the lines, making it look more real (thanks Jen for suggesting I blur)
6. Now fill your bottom layer (Layer 2) with the colour you want your dog. I am choosing reddish brown
I unselect the insides of the dog and flood the whole layer.
7. Now the fun part, go back to the second layer (Layer 3) and play with the opacity setting untill you can see the main background colour, and the brindle is fainter. The overall dog will not be the exact same colour. If you fiddle with different colours you can get all differnt looks.
8. Your dog is finsihed. Save the image as a copy. Then you can just delete the bottom layer and change the dogs colour. That way you don't have to set up the brindle part again. Its much faster.
And that, is how I make Brindles in Aboobe.....
What about the white markings?
9. So your dog doens't look cool with no white makrings? Easy.
Add another layer. Put it between the brindle layer and the top layer
10. Choose white, then the airbush tool. Airbrush on your white (or other colours) markings. You can mess with the airbush settings to make it bigger or smaller, smooth or more blurred. Make sure you have the "white markings" layer selected
11. Save your dog as a copy.... and walah, new dog. You can then just delete the white layer, add a new one and make new markings
Oh, I forgot say, when you save these as a .jpeg that you will loose the layers, but that is what you want. Then you can open the .jpegs and make them .gif with transparent backgrounds, or just leave them .jpeg
and THAT is how I make Brindles in Photoshop.......
Hope that helped. I am still learning so you might find a better way, but this at least should give you ideas if it doesn't work the way you would like.