Despite the fact that I crossplay as a Red Medic, I can't offer any good advice on making yourself look less girly. I have tried experimenting with make-up, and ultimately there is just no way to give myself a nice square jaw, and let's face it, most of Medic's face is jaw.
As for the Sniper, The sunglasses hide your eyes nicely, which does help a lot. It's also a good idea to use some make-up to put stubble on your chin, but you probably already knew that.
As for the sunglasses, I'd try finding a big pair of sunglasses that look like what the Sniper wears and try them on over your regular glasses. If that doesn't work, you could probably buy some transparent black fabric from the fabric store and stretch it over your glasses, although I don't know what to suggest for how to secure it to your glasses themselves (I know I wouldn't want to try duct tape, for instance).
Costumes In Progress:
Pink Ninja Ranger (Mighty Morphin Power Rangers: The Movie)
Blu Soldier (Team Fortress 2)
Griselda (Odin Sphere)