Well, I've done this one several times, so here goes:
If you have not already done so, grab a few of the sculpting tutorials over in our
Conversion Workshop and bone up on the basics of sculpting.
The number one rule is patience. This
will take a while.
1. To begin with, you need to get your blob of Green Stuff (not too much of it) and carefully pull it into the general shape of the cloak you want. If you want a hood (for others who may look at the thread) don't put it on now, it's the last step.
2. Carefully, carefully put your GS onto your model, making sure that the wider end is down. Now try to pull it into the general shape you want the final result to fall. Don't worry if it doesn't go perfectly, you'll build up on it later.
3. Here's where the patience comes in. As our dear Ebob would say,
leave it alone. Put it down and walk away for a while, at least for six hours - though I recommend longer until you're experienced with shaping GS. Work on painting other models, read a book, play ball with your friends. Whatever.
4. Once you're sure the GS is cured, mix up a little more. You want to apply this along the edges of what you've already got in small amounts (no more than half the width of your pinky) until you've got the thing as wide as you want it. Be sure to let the stuff cure between each of these stages.
5. Once you've got the basic shape, use a blob 1x to 2x the size of your model's head to cover the back. This is where you really get to shape your cloak to look the way you want it.
6. After that has cured, take some GS about 1/2x to 1x the size of his head and smooth what of the underside is showing. Don't worry about being to exact on this side, because it won't be noticed as much AND too much pushing away may free your cape from the mini. This step is just to cover over anything blaring obvious.
7. After that's all done, take a little blob of GS and touch up any changes you want to make to the cape's general appearance.
8. (Optional) If you want a hood, all you need to do is decide whether you want it up or down. If up, just sculpt a little bag onto the top and back of your mini's head and smooth it down - you will shape it the way you want it as you do this. It won't be hard.
If you want the hood down, grab a blob a little smaller than your mini's head and put it at the back of his neck. Use your tool to press an indention where it meets his head, and follow up with some pressing on the outside to make a more hood-like look. This can be a little tricky, but persistence will give you a perfect hood.
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