My understanding is that pasty butt is caused by them being too cold - has nothing to do with the bedding. Try turning up the heat a little and see if that helps?
For some reason only my silkies get pasty butt. Clean them off well with a warm paper towel. Then take a q-tip, dip it in olive oil and apply to the vent area.
I've had 2 slkies get it. The current one is in with ameracauna/cochin crosses and the last one was in with Marans. Only the silkies got pasty butt. Weird.
I've only brooded two hatches...well, I'm two weeks into my second...the first batch were Serama's, and the newest one are Silkies. I keep the temp a bit higher then needed the whole time, but they have plenty of room to get away from it if they want, and I've had no one paste up on me at all. I use paper towels till they get the hang of where the food and water are, then just pine shavings.
I have to agree with riftnreef, paper towels for the entire first week. Then I go to pine shavings. I also use horse beding pellets. They actually are more absorbent that even the pine shavings are and don't tend to foul the water near as much. Good luck with all your babies.
I think more people would say pasty butt could be caused by the temp too high versus too low. Mix a little yogurt ( plain with live cultures in their food). I had a terrible time with it and someone suggested putting a little bowl of sand in the brooder. Haven't had a problem since!