Surface editing to create angular deformities


I am looking to 3d design and print this car from Wacky races.My plan was to make the shell of the body using regular surfaces and then use control point editing to make the rough boulder surface on the outer shell of the body. I was thinking of using control point editing to distort the surface, but I want the distortions to be angular rather than smooth so it looks like the surface of a rock or boulder.How would I alter the settings in the edit function to create angular deformities rather than smooth ones.
The other option I looked at was using the mesh functions to make a simple mesh and then move the vertices of the mesh to create angular deformities in the surface?