For Kato lettering and all the markings, stripes, etc painted over the base color of the car the best product is "Mr. Hobby Mr.COLOR Thinner 50". I think a friend got this from Japan direct (big clue -- the name is the only printing on it in English, rest is Japanese) but it's amazingly effective, 100% removal with only a slight dulling of the car color. I used it to remove the incorrect stripes from the baggage and RPO on the first-run PRR pass car sets and you can find no trace of them.
Apply small amounts of the thinner with a small brush directly to the markings you want to remove. Let it sit about 15-20 seconds, then swab with the brush to see if the paint is dissolving. IT's pretty quick-acting. I trace over the markings with the brush to loosen them, and wipe it off with a clean cloth or paper towel. Re-apply as needed to get all the traces off. The thinner doesn't do much to the car body color, but it does dull it a bit. Because that gives the old paint a little tooth I find this makes a great base to just paint over rather than trying to get all the paint off the KATO car. You can strip a BN car down to just plain green or a PRR one to plain brown, then spray your new color(s) over that and apply decals. The KATO paint is so tough to get off I figure that's perfect for my final color to stick to and never wear off.
After all, the real RRs just sprayed over the old colors whenever they re-did the paint schemes on their equipment.
Also I heard somewhere that KATO uses soy-based paints on their products. Don't know what stripper that stuff needs.
