Creating Your Own 'Dirt' Brush

Step 1:

Open a new document, the size doesn't matter. Make sure that the foreground color set on black #000000.

Step 2:

Pick the 'brush tool' and press on the arrow next to the tool pic on the left side of the bar. Then pick "Chalk build up".

Step 3:

Set the "flow" to 73%.

Step 4:

On the right side of the bar, there is a little pic, looks like a document. Press on it.

Step 5:

Do the following:

*Its ok if u don't have this texture, pick something else.

Step 6:

Now, draw something on your work space. It doesn't matter what, but it shouldn't be a clear shape. It has to look like dirt. Here is what i've made:

Step 7:

After you'll finish bruwsing, go to Edit>Define brush present. Name it and press OK. Now you can use the brush every time you want.

Have a nice day!