Prune Juice - help!

[MummyMellie]

4mth old DS in need of a bit of help in the going regularly dept and prune juice has been suggested, but can't seem to find out how much to give him and how often, any ideas?
Have bought him some additive free organic stuff but wouldn't mind making it myself from dried prunes, does this work as well and how much cooking/soaking do they need?

[funnypeculiar]

soak them overnight in water (I pour boiling water over them). I think someone on here recommended 2/3 oz of fairly dilute juice to me. well to dd