on average they start laying around 24 weeks but can be anything upto 35 weeks.
all bedding should be dust extracted so use dust extracted shavings, hemcore, rapport or similar. Get them perching by going to their coop when they are sleepy and lift them onto the perches, they do an awful lot of poohs over night and this could lead to infections if they are sleeping in it, plus you will get mucky eggs.