The best thing you can do is wash baby's hair less often. Natural oils from baby's skin and your fingers is the best thing for baby's hair. Other than that, try a leave in conditioner...Suave makes one, Loreal makes one.
well, my son has cradle cap again at 22 months - well he got it again at 17 months but its itchy and scaley, the ped said I should use head and shoulders and after 3 washes in 2 weeks its totally better. just be careful cause its not baby tear free . I would only wash my sons hair every 8 days and his still got nasty itchy so I moved it to every 3-4 then every 2 weeks - ddin't matter.
My LO had cradle cap and my ped suggested Selzen Blue- it has a certain ingredient that head and shoulders does not (sorry cant remember the name!) that helped some but eventually we had to get a prescription shampoo and had to use that every other night. That worked wonders :)