If you are looking for a product that will just darken the rubber and leave a matte finish I would recommend Ammo Mud tire gel. It basically makes the tires look brand new again without the gaudy bright shine that doesn't belong on a truck but to each their own! I hand apply it with an applicator to work it into the tire and all the lettering and design on the side walls.
Its a little pricey at $18/bottle but the bottle lasts me all year doing the truck and a car every couple of weeks.
There is absolutely zero sling if you follow the directions and it lasts for a couple of washes or a few weeks.
I have learned to stay away from the aerosol products because it gets everywhere, the rim, the wheel well, body, etc. so you may as well be hand applying with the cleanup!
https://www.ammonyc.com/shop/ammo-mud-tire-gel/