[WendyA]

I'm fine with men's dress shirts, I've tried to use women's, but a vast majority have princess seams which are a dead giveaway as well. I've found women's polos to work fine so long as the placket (button area) isn't excessively long. Hardly anyone notices that the placket is reversed from a men's polo.

For underneath I use women's sport tanks with compression/shelf bra built in and that's been working for years now.

Yes, I agree about the Polo's.  Usually, they are short one button or the buttons maybe closer together.  But, I have never seen anyone run around with a ruler or count buttons.  LOL.

I think the issue with Polo's isn't the number of buttons it is that the longer run of buttons or lower cut are designed to separate the breasts and make them even more prominent.  If you are trying to present your breasts then those shirts are great, if on the other hand you are trying to hide them then probably not the first choice of shirts.