How do i get flour off a cockatiel?

I had just got done making cookie dough and my cockatiel was bathing in the sink when I dropped a bowl and startled him. He took off flying and of all the places he could have landed...he landed in my flour container! I tried to rinse off the flour, but can still tell there's some on his wings and underside and it is stiffening up...is there anything I can do? He is trying to preen and I don't know if that's a good idea? Thank you for your help.