Looks much better than before. I actually experimented a little bit last night and it's really a bit tougher than I would have guessed

. I recomend doing two snow layers, one for a frosty look and one for actual acumulated snow. The frost layer will have a bit of opactity, but make it irregular, so some parts that are almost transparent and some that are less so. (A good job with this will look very nice over your paper I think) Your snow is quite white too, I think for ingame purposes, you may want to get it a little darker and with some more blue. More granulation too, that will help make it look more natural.
Using the burn tool was a bad suggestion, I couldn't get a good look with it at all.
Also, as with adding dirt and grime to clean textures, the irregular brushes are your best tool, use them for pretty much everything including erasing and lightening the opacity, even with the burn tool if you can get some good results with it.
Keep it up!