About 6 months old I'll let them have a look in, and a rag on the carcass.
Another thing I'll do with younger pups is take them a brush home, let them have a rag on it, take it off them, then hide it in the garden, and then I'll let out again for them sniff it out.
I'm not saying it's a must do thing, but the pups always enjoy it and I like seeing them using their hooters trying to find, It's a good craic to watch.