My son had very very bad cradle cap, he's now 4 months old and it's nearly gone, I tried oil, shampoo, all sorts of different bits and it just made his head sore.
In the end I used Cetraben, his eczema cream available to buy off the shelf, left it on for an hour before the bath, washed his head with a soft brush and shampoo then combed it out.
The cream made it so soft that the dry skin just peeled off! It's taken about a month and his hair came out with it but it's worked!