You simply wipe it clean. There are two perches in each cage of different shapes and size. These are scored to assist the birds to grip them better. I believe the different types of perching cause the bird's feet to constantly adjust their grip on the perch. This helps prevent sores on their feet.
Square perches are absolutely essential and also assist the mating process.
We also use a nursery cage on wheels. It gives us somewhere to put the young birds. You can push this around when tending to your birds. This helps steady them and the nursery cage also does not take up valuable breeding space. We clean all our flights and cages daily, as deep litter is a method I cannot agree with.