We use paper towels the first couple of days, then pull them and pile in an inch or so of pellets. I leave them an open space in the beginning so they can scratch as that's the only downfall, their little toes can't scratch them. After I see them scratching through them, I just put them over...
Next time you do this, I'd love to hear you try using horse bedding pellets. I think you would see a huge improvement. We use those in our coop and do nothing for a year. No maintenance, no smell. The pellets absorb everything and dry out the poop.
We have silkies which develop slower than yours and I've had mine outside in those temps at about 2 months old provided they are protected from wind. We have a cozy coop radiant heater in a hutch they snuggle up in at night. Sometimes during the day they go in to warm up and come back out...