My 4-month-old had really bad cradle cap. Following the pediatrician's instructions and my own previous experience, I rubbed olive oil on his head, let it sit for a few minutes, and comb it out. Then, I washed his hair with Head & Shoulders Dry Scalp shampoo (that was the ped.'s recommendation) and massaged Aveeno baby lotion into his clean, dry scalp. It was amazing! The cradle cap hasn't been bad since. When his scalp starts looking dry, I use the H&S again. I always do the lotion, no matter what.
I've used Playtex drop-ins for all three of my boys and very, very rarely have a problem with leaking. I use the bags that you pull over the top; I've had better luck with those than the pre-formed drop-ins. As long as I make sure the nipple is pulled all the way through and screw the lid on tightly, they don't leak.
My boys are sloppy drinkers, though, and always leak from their mouth. I just tuck a wash cloth under their chin for every feeding to catch their mess and then toss it in the wash.