Also grabbed an old painting brush and bleach. After taping the jeans, I started with the paintbrush to put bleach on it. The cardboard you can see on the first picture is handy, because otherwise the bleach will reach the back of the jeans.
After i think 10 minutes bleaching I washed the jeans and put it in the tumble dry. It's just turned out great! I would expect some mistakes, but it's quite well done :)
So if you have an old pair of jeans, or your boyfriend or so, just grab it and do with whatever you want!