Removing Rust-Oleum Paint from Clothing?

My husband came home with his work pants covered in Rust-Oleum! It had already dried so I'm not sure if there's anything that I've seen on your site I should try. As you suggest several things for paint, which do I try first on this? No clue if it's oil or water based or even which of the products it was other than it had been spilled all over the floor and he had to try to clean the floor. Any ideas would be gratefully accepted!