I'm DMimg my first session this weekend and I need to make at least a couple of dungeon maps. We're playing tabletop and I would like something close to the way the grid on Roll20 works. I'm trying to avoid hand-drawing everything on graph paper. I don't need anything elaborate, just something to keep track of movement in battle.

I have Photoshop CS2, which is my favored program as I've been using it for many years (I started with PS7 waaay back in the 90s), Krita, and Painttool SAI. Any suggestions? I've gone through the tutorial section about 25+ pages but there is always the chance I missed something.