Adriana learnt this technique from school.  Slop some paint on some marbles and then roll them around the paper, with the paper folded and tucked inside a shallow box. The top ones are mine. Adriana's is the bottom one, but she did some others as well..

The painting below was made in the back yard.  This was to be one small, but seriously worked on, piece for a patchwork.  She stood back and flicked paint with the brush towards the painting and the grass and leaves it was sitting on.