Garden or Recycling Art

I am currently trying to create styrofoam vessels. The idea is to use materials such as packaging styrofoam blocks  and shape them with heat into interesting forms so I can use them as planters.  I have sprayed the finished object , so far I have only made one, with acrylic paint. The first piece looks great but I am looking for a more textured surface. I am just wondering if anybody has tried something similar using textured paints? Since outdoor art is not my normal medium I am trying to avoid big mistakes.  Any hints and tips are greatly appreciated?