I started with clear nail polish and then went on to pinker shades, tinted lip gloss, face cleansers (have a really good one from Lush), moisturisers (God, try them all). The good thing with cleansers and moisturisers is that they are invisible to anyone else.
In guy mode, I now just say it is for me! Money speaks. I even went into a department store a few months ago and told a cosmetics girl that I didn't have a clue and she sat me down and we tried stuff to get the colour right. In male mode. In a suit. At lunchtime with crowds around. Enjoyed myself too. Left the concealer on 'cos I looked better! She made a sale and I got a freebie bag too!
I have also recently upgraded my glasses and told the optometrist I was MTF and need girly frames. She got a bearded guy to assist. Very amusing! Funnily enough, some people I have disclosed to have been flattered that I felt OK to say something. If they aren't, go someplace else.
Emma