Hello, let me help you a little!
There is no such expression in brazilian portuguese as "deitar luto" nor "usar luto". "Luto" means grief, if you are grieving for someone who died, then the expression would be "Estou de luto". Check this example out: "Eu estou usando preto porque estou de luto pela minha avó." Meaning "I'm wearing black because I'm grieving for my grandmother."
The brazilian portuguese does not have a specific word for the grieving clothes, we just say we're using black. However, in a funeral, the dead guy's clothes have a specific name, "mortalha".
I hope it helped, tchau!