I saw this activity at Chasing Cheerios the other day and couldn't wait to try it! I froze a few of B's toys in a bowl of water and let him use his tools to get them out. (Run cold water over the plastic bowl to get the ice chunk to easily fall out)
The hammer and chisel method is what we were teaching and hoping he'd use, but in the end it was just the hammer that B had the most fun pounding away with.
Luckily, I froze two bowls because the first one was too deep and solid for him to break. My husband did all of the breaking while B waited along side him to get the toys out with his pliers. The second bowl was shallow and easy for B to break with just the hammer.
I don't know why I wasn't prepared for this part, but there were ice pieces (big and small) flying everywhere! We would have done it outside if it wasn't so hot (over 100 degrees). Today I froze a few more bowls of "treasures". Each time he tries it, he gets more comfortable and independent with the activity. Loved it!