I'm one of those who focus more on blending than passing. In either case, I judge my success in passing/blending in terms of distance. In general I don't draw attention at 20 to 50 feet (except for a couple instances over the course of 5 years where people pointed or commented from across a parking lot). I think that at 10 feet people can tell there is "something different" about this woman. At 5 feet or less (like across a retail counter) there's no doubt that I'm a man in a skirt. I can live with that.
The "tells": eyebrows and the set of my eyes, bulky arms/shoulders, voice (definitely), hands, and any number of mannerisms that might seem out of place or unnatural.
Don't stress about passing. Just go out and feel good about yourself in your non-guy world.
