I found another thread about using a flour and water to make a paste and then you use the paste to paint a mickey head on the shirt. You let that dry and then you use spray paint. Once the paint is dry you wash the shirt it kind of looks like a tie dye shirt.
I wanted to try something different so I found clip art of a skull and cross bones to make pirate shirts. I used the paint program on the computer to make adjustments and ceated a template. I then used a fabric pen to trace my pattern onto the shirt. I was not able to get the flour and water paste correct so I found a Color Block by Tulip (it was next to the spray paint) and it worked great. Word of advice: I was trying to save the Color Block and put it on thin, well my spray paint went through. I went back on my sons shirts and splattered paint randomly to make it look like I did it on purpose.
However, the boys loves there and thinks they still looks cool. These are my sons shirts.
Here is my shirt it is still drying.
Hope this helps!