Whatever treatment you try (teabags, distress ink, sanding) try it on the extra cards first, if you still have them. The finish on the cards can make a big difference in the results. If your chosen treatment doesn't look good, then at least it was just a spare card.
I used distress ink on a RWS deck, but the slick finish on the cards kept it from staining them. I had to really blot it on to get it to show at all. Even then it tended to bead up. I sanded the cards with extra fine sandpaper, and then the distress ink just collected in the scratches. Those U.S. Games decks are kinda indestructible.
Another method people here have used is dunking the entire deck into a mug of tea. Then they blot the cards on towels and as they dry out, they gently shuffle them one way and then the other, to keep them from warping. I haven't tried this yet.
Here is my thread about aging my deck. There are a lot of links within that thread to other threads, talking about various methods including the tea-dunk.
http://www.tarotforum.net/showthread.php?t=150377