Shelf liner with shavings on top. Shelf liner is washable and resusable and gives a good grip for chicks.
Hope your rooster gets better. Vitamin and mineral deficiencies cause a multitude of problems in hatching eggs and growing birds. Sometimes feeds are lacking proper concentrations or the feed has been stored too long and potency is gone. Highly recommend you find a supplement that has a vast array of vitamins/minerals in it. Avian Super Pack is a powder for birds to put in their water. One pack will treat hundreds of gallons so you have to use just a small amount per gallon. Sometimes feed stores carry it, but I purchased mine online.
Where did you put the harness on his legs? Should be but below his hocks not above.