I just did that this weekend. Previously I've dressed androgynous or partially (I.E. no makeup, so beard shadow was obvious, or only in a very safe place like my therapist's office). I forced myself to do some routine shopping.
What did it feel like? Scary as all. But frankly, nobody did anything horrible, and I got no more than one stare while out. I dressed pretty casual and conservative - jeans, a feminine but not frilly or sexy top, a pink cap to cover my way-too-short hair, makeup that might as well be stage makeup to cover my beard shadow but done as much as possible to appear natural. I definitely wouldn't make all the guys do a double take or win any fashion awards! I was kind of going for "don't stick out", although I'm sure I still did and I'm sure I was anything but passing. But as awful as I must have looked, nobody said anything.
What got me through it, and even smiling once I finished, was that I reminded myself: Nothing bad is happening, and this is basically the worst you'll ever look and feel dressed, it's going to be easier than this next time.
And how I see it now? I'm making an effort to be myself every weekend going forward. It is so worth being myself.