How do you cover a styrofoam ball?

Hmmm, not sure and since this website is All Things Plants, unless someone here has any experience with it, I don't think this is the best place to find an answer.
Wait!
A quick Google search brought up a thread right here on ATP so go ahead and ask the original poster by adding a post to the bottom of that thread or contacting her directly by clicking on her user name and using the 'Send goldfinch4 a Tree-Mail' option.
The thread "QuikWall Art and Cement Tutorial" in Garden Art forum

And to ATP!

@goldfinch4 is definitely our resident quikwall expert!

Hi jalberghini, welcome to ATP !

An easy way to cover a styrofoam ball with Quikwall is to make a rather thin slurry and work that into the styrofoam by hand as much as you can. After that thin layer is worked in, I then add a layer of thicker mix over the top. The thin mix "grabs' the styrofoam, then the thicker mix grabs the thin layer. If you have any other questions, I'm more than happy to help.

What are you planning on making?