You can doubly reinforce the praise by offering one of their favorite treats. I always bought men's short sleeve shirts at thrift stores and wore them over my T shirts. It didn't matter if the thrift store shirts got stained or not. Back in the day I used to run home at lunch to check on my then birds and one day I forgot to take off the bird shirt and wore it back into work. With a huge poop on the shoulder. Nobody even noticed, LOL.