The next step is to fill in the less complicated areas of the selection. Go back to full RGB by clicking the RGB (or use command- ~ if you are cool). You go back to RGB because it is easier to tell what you want and don't want in this mode. Using the Lasso Tool (after disparaging it in the last lesson) carefully draw around the edges of the less complicated areas of the selection. Stay as close as you can to the transition zones (see below) because it makes your work a lot easier when we get to the next step. Keep in mind that it is easier to select smallish areas with the lasso tool and then add to it by pressing the shift key rather than try to select the entire area in one swoop.
After selecting the desired areas fill the selection with white. Go back to your channel by selecting it in the palette (or pressing command-4 if you are cool) and then choose Edit>Fill from the menus. In the dialogue box, select white and press OK, the area within your selection is filled with white (which means this part of the image will show through when we convert this to a mask)
Next, do the same with the area of the image you want to mask off. Select the areas of the image (in RGB mode), making sure to stay out of the transition zones. Fill it in the same manner as before but this time select black from the Fill dialogue (also make sure you are back in you channel rather than RGB mode).
Lastly, go back over your edges and make sure they are clean. There is usually quite a bit of noise remaining in the image, which can be removed with the Paintbrush Tool. Paint black over the areas you want to mask (make transparent) and white over the areas you want to keep. Be careful not to ruin your transition zones. I have found it is best not to do too much around the edges or they will turn out unnatural. There are often areas in the hair that are ill-defined (usually the wispy ones), usually you can remove these (paint them black) without an unnatural-looking result. Often you will have a hard time deciding what to keep and what to paint out, if in doubt go back to RGB mode and get your bearings.
