Billboards are giant boards placed throughout the city that have the words, "Your advertisement here FIZZCO." You can easily spot them in game if you get close to one, and they are usually where normal advertisements would be in the real world. To deface 40, all you need to do is approach each one, and press
to "Deface Ad." Pressing
will cause you to automatically spray paint a red robot with the words, "Dominated."
Now, the game does a pretty good job of providing you with collectibles maps. They are easily purchasable with Overcharge, but I like saving my charge for better weapons. So I went and searched online for an awesome map of all the Billboards.
Here is a link to the map:
which is from the website:http://segmentnext.com/2014/10/29/sunset-overdrive-collectib...
But if you still want an in game map for convenience, and don't mind wasting overcharge / have too much of it, you can go to Two Hat Jack, found in any hide out and other locations in the city.
To purchase your own maps, all you have to do is hold
on Two Hat Jack, hit
, and scroll through the list of maps for each and every collectible.
Below is a video showing you the pricing of all the collectible maps and every single one that is available for purchase.