ok a tip about using the brush - you don't need to use tip of bristel at all time - for edges - actualy the side is better then trying to use point and usualy missing - the side of bristel will just slide itself on Edges hihlighting them nicely
Face - meybe some well controled ink ??
Snow - you may buy ready to go snow effect , but Salt - well thats interesting idea
i actuly used as snow a baking soda, never tryed a salt due to it corrosive properties - but well hey i is alvays a first time

so if you gona experiment more with salt - crush this one you are using to a smaler crystals - for better effect - and mix it with gloss Vernish as medium - this should give an effect of glossy fresh snow or get you an effect of : sloppy and muddy wet looking
like on base below - jest a lot of glossy vernish into the mix
Click to see full-sized image
o and try to randomize look of rocks - get some big ld brush and jut applay a random shades to the grey rocks .... duno how to describe - but plain grey rocks looks like concrete
maybe someone else explain this better ..