Painting inside cowl ?

If you don't mind doing a little cutting you can cut a hole large enough to get your arm in there to brush on some undercoating. It's best to make the hole on the outer cowl where the door and fender cover the outsides of the cowl. Then close it back up and it should last forever. Use a stick with a brush attached to reach all the way in there. Some people don't like cutting it open but nobody like rust in their cowl!!!