Well, I'm not sure that anyone so far has actually had really big 'guy hands' ... I mean, I take a man's medium glove and my hands are almost exactly the same size as my wife who is 5'6" and very slender and feminine in appearance.
So anyway, I measured my left hand and it came out at about 7.5" long (maybe a little more: I wasn't entirely sure where on my wrist to start from) and 4" wide ... which is pretty much the same size as all the girls worrying about their 'STOP sign' hands ... And my best male friend's wife was only the other day pointing out how much thicker her wrists were than mine, and no one would ever mistake her for a man.
So I think this is another one of those things that we are super-conscious of, but that disappear as an issue of ones presentation as a whole is confident and female ... Yes, pretty nails will make a big difference ... And of course, Pauline is right. Guys aren't ever going to waste time checking out a girl's hands ... not as long as she has boobs to look at instead! 😉