Tires

For a start, you should sand the tread surface to remove any mold lines and gloss. Inside the actual tread pattern will probably still be shiny but applying a little clear flat acrylic (MUST be acrylic) should fix that. The sidewalls can also be dulled with fine sandpaper but sometimes this can't reach some of the detail areas so clear flat acrylic is needed again. Another method that some people like is scrubing the whole tire with a scouring powder like Comet. If you're going for a "dirty"  look, you can apply an earth toned wash. Once again, it needs to be acrylic because that's the only paint that will dry properly on a vinyl tire.