Regarding fog of war: I use Paint.Net, although Gimp/Photoshop probably work similarly. I open the map for editing, then create another map, totally black. I then copy/paste rectangular sections from the master map onto the black one as layers, one per room/area.
When projecting the map, I do it within Paint.Net, which keeps a small control showing which layers are/are not displayed. I move that control down to the lower-right corner of the laptop screen (you only have to do this once, then it stays). I put a small DM-Screen style wall around this control as it appears on the tabletop, so the players can't see it.
On my laptop, when they enter a room, I simply click that layer on (I number them to match the room descriptions) and that room gets added to the displayed map. You can even click off the room they just left.
Works like a charm, and the editing gets much simpler with practice.