I use water and a microfiber towel to clean off the majority of paint off my mask and then if I want to give my lenses a really good clean I use any type of lens cleaner (The cheap lens cleaner for glasses and such).
At the field, I use a spray bottle of water and micro cloth. When I get home, I fill a sink with water and dish soap and let it soak for an hour or so. (after you remove the lenses of course). Then I pull it out and dry it off with micro cloth.