That's a good scheme. It's best to stick the manure in a sack, then the bits don't bung up the holes in your watering can. Just squidge the sack once in a while with something blunt to extract the lovely juice into the water. Another brilliant feed is obtained by growing a patch of Bocking No 14 comfrey. You can harvest the leaves two or three times a year and soak them in your barrel for a few weeks. Keep the thing covered and keep poking the leaves down. It stinks to high heaven but, when watered on your crops, it has an amazing effect. Stinging nettles are almost as good, but you should use them before the seedy little tassles form.