I use P&S shampoo, and when the scales are thick on my scalp, I use the P&S scalp treatment. If use the shampoo at least every other day, it usually does the trick and it's not tar based and smells pretty good, which is why I like it.
The only time I have to use the scalp treatment is when I've been sick and haven't been able to wash my hair daily like I usually do. Then, I dump it on at night after showering & washing my hair with the shampoo, then put a showercap on my head and go to bed (thought I don't think I'll do that anymore in light of Keith's info). If I don't want to sleep with a showercap on, I wait 'til I'll be home all day. Then I shower, wash my hair with the shampoo, dump the liquid on and wear an old shirt so if it drips, it doesn't stink up anything. The scalp treatment is stinky, but not really unpleasant, just odd. After a minimum of 5-6 hours, I go back in the shower and wash my hair again with the shampoo and voila, my scalp is much better.
Getting Adam's scalp very very wet is important for the treatment to work. Plus, the stuff washes out much easier than I think lard would. One bottle of the scalp treatment lasts me up to a year, which is good, because it's $18! You can buy the treatment and shampoo at the pharmacy, you just usually have to ask for it as they typically keep it behind the counter. It's made by Baker/Cummins if they have to order it for you. The shampoo costs between $7-$8 and you really don't need that much shampoo, either. When my hair was really long, I still didn't need to use that much, maybe enough shampoo about the size of a nickel.
A fine toothed comb is a must to get all the loose scales off my hair afterwards.
I am female, and was born in 1972 with Lamellar Ichthyosis.