Barleywine
I don't know how good a general Tarot dictionary would be for the Thoth since it's all contextual. A symbol found in the RWS could mean something similar in the Thoth, but its application and context could be entirely different. Per the example I gave before, Crowley's take on Cain and Abel is completely different from anything I've ever read. That may say a lot about my own ignorance, but Crowley uses symbols the way Humpty Dumpty uses words, he makes them mean anything he wants them to, albeit with reason and intelligence. He can, at the very least, explain his process.
I've found that a decent dictionary of symbolism - like Cirlot's - to be of some use in this regard. You still have to make the cognitive leap between symbolic universalism and "Crowley-ism," but I find it occasionally insightful.