Paint it. Everything. Prep the block like you would for maximum adhesion. Oven cleaner works well. Dry, wipe and dust spray immediately. Paint all your machined surfaces. Rust o leom. When you're ready to build it. The paint is easily removed from the machined surfaces with lacquer thinner or...
I found cats usually spray. Using hand sanitizer as in common Covid sanitizer removed the odor. I believe a black light will show the specific areas and concentration...