Everybody has their own way of creating great looking hair. What I offer here is one of my favorite techniques. It is very easy and fast. I am sorry, but if you use MS paint this tutorial will not be any help to you. I am illustrating this tutorial using PSP ver. 7. I hope you enjoy it and find it helpful.
First choose New Raster Layer from the Layers menu then give name the layer "hair".
Next, create an outline of the hair in the darkest shade that you plan to use in the hairstyle. I have provided some hair color palettes here.
Now select the hairstyle with your magic wand and fill it with the same shade as the outline, using the flood fill tool.
Next, under your selections menu, choose MODIFY/ CONTRACT
Contract by 1 pixel.
Using your flood fill tool, fill the selected area with a color that is one shade darker than the first color.
DO NOT un-select this area. This is the area we will be working with for the rest of the tutorial. Using the dark shade that we began with, create some lines in the hair where you would like to show depth. Also make sure to draw a part in the hair with this same dark color.
Now you will choose a third shade that is lighter than both of the other shades we have used thus far. Draw some more lines in the hair where you would like to show some highlights. I have widened the darker lines in order to give even more depth.
Now we are going to add the finishing touches. From the effects menu, choose User Defined. Highlight "Sample Blur" and click apply.
See! It does all of the shading for you! You can also achieve this very same effect by using the gaussian blur or texture preserve smoothing in step 8. All 3 methods give you pretty much the same effect so it is a matter of preference.
Here you can see how it looks scaled down to regular size.