I think the "A" in that number X-20A means acrylic. If thats the case, no, it shouldn't affect lacquer paint at all. If you use an acrylic wash, you should be fine.
As far as ratio, I don't know for sure, I just mix it till it flows nicely. Probably something like 20:1...pretty thin. I always keep a bottle of black wash ready. If it starts getting too thick, I just add some more acrylic thinner. Hope this helps.