If you had disease problems disinfecting is needed, but as oldhenlikesdogs stated, a good clean is just fine. Disinfecting can't hurt though, you can buy any of the common disinfectants from a supermarket but I use a stronger industrial grade disinfectant called Virkon S. It is very effective. I would recomend disinfecting if you are introducing rather young pullets as older birds can carry disease that young chooks can't handle. Turkeys can carry Blackheads, commercial meat birds can carry mycoplasmas ect. Good luck with your poultry.