This is the good point for accessorizing, before you continue adding more details and color. I wanted things like pants, shirt, a belt and guns. In Fig.06, you see the shirt painted on top of the model. To do this, you basically need to mask the part you want to turn into clothing, select the Standard brush, set the stroke to freehand and, by pressing ctrl, paint the mask where you want it to become clothes.
After finishing up the mask where you want your clothes to appear, you need to go to Tool/Subtools palette and press extract (Fig.07). The size of the extract depends on a couple of factors, so if your clothes extract too thickly, you can delete that subtool and try again by adjusting the thickness setting.
Give your new subtool an appropriate name so that you don't have problems later if you decide to make an entire subtool tree into one mesh or any other complex subtool operation.
Also, the newly extracted subtool is extracted at the subdivision level from the original mesh. The lower the better, but if it's too low then it may become inaccurate. It just depends on what you want to do with the model later.
If you intend to export it with all its subtools in a third party application for say, animation, then you would need to keep your polycount within a reasonable count. If you are staying in ZBrush, then you can be little bit less concerned with the poly count.
Fig.08 shows all the subtools created and refined. The guns were modeled outside of ZBrush. When you've completed all the subtools, then you can carry on applying more details to the base character.
I have couple of customized alphas that I created myself. Once I'd decided which ones were the most appropriate I set up my brush. Specifically here I have used the Standard brush, with the stroke set to DragRect, and my preferred alpha. Z intensity was about 10- 14 set to sub. When the brush was setup, I started dragging texture rectangles across my model (Fig.09).
Fig.10 shows how it looked at the beginning of the whole process.