mum has asked me to make a picture 'winterlike' so it can be used for a xmas card.

have found a tutorial of gary's (excellent as always), a december one, cant recall what year off the top of my head but, in it he shows how to make snow falling,

one down, one to go - want to make it look in the picture that it has already snowed, ie, snow sitting on ledges - i (being the extremely novice person that i am) am thinking of approaching this by using the shape editor tool, drawing shapes of where the snow would be lying, filling with white and feathering. has anyone got any better methods or ideas of making this effect?