i looked at it with a flashlight and i doubt a wire brush is gonna get this clean enough. the fitting just will not budge period. i even had vise grips on it and it still wouldnt budge. it's not a big deal to me, it's just a hard line and it's not the end of the world. i've been wanting to upgrade the entire brake system from the lines up anyway. i didnt want to replace a line THEN do the upgrading. i dont have the money to do a stainless steel kit right now so i'll have to replace this one line first. again, not a big deal i just find it annoying that little window was there in the right place to ensure the end of the hard line corroded and rusted. i'm not even sure why it's there since i cant get a flare nut wrench through it as it's too close to the floor pan where the back seat is. after this i'm blocking off that hole to prevent this nonsense from happening again.