Now that you have your folds, it is time to spray paint. You will need to do this outside as with any spray paint project. This gives you ventilation as well as a place for any overspray. Just put the cardboard with the shirt on top in the grass and spray the front of the shirt first. You can do one color only.
Or you can do a mixture of both colors. For my two-color version, I sprayed pink, then blue, then some more pink, and finally some more blue. I didn't wait for my colors to dry in between coats so I got a slight mixing of colors. You can wait for the colors to dry for a different look if you would like.
Allow the front to dry then flip the shirt over and repeat the same painting procedure on the back.
I also repeated the two-color design on the back of that shirt.
Once the shirts have dried for at least three hours, you can unfold them to see the results!
I am not sure which design I like more as they both turned out great.