cupafful, I haven't tried it, but I read advice somewhere about making a small roll of foil and putting it inside the mask so that you can fit it over your nose. It then should fit more tightly and not let your glasses steam up so easily. I find that if I put my glasses on firmly over the top of my mask that helps, but some days, when it's cold or damp outside, you are probably going to steam up whatever you do!
Callistemon, I have found that the steam from my Christmas sprouts, which have, of course, been boiling away for several months now, is keeping my kitchen permanently steam-cleaned, so that saves a bit of time.