Hey,
to all of you pro's, this may sound very obvious but i have found a great way to make realistic rubble. I am currently redoing my sis's bedroom and we had to redo a socket, and we had to knock some of the wall out and i'm not surre whther its the same in the US or other countries but we have like a layer of plaster over the bricks and stuff, so when we knowcked it out all of these random pieces of rock and brick came out all different coulours (realistic ones though) along with loads of dust which looks really convincing.
If you already knew sorry, but to anyone who doesn't know i hope this helps
Thankyou