Drawing dungeon maps like on this video

[dotheminimum]

Hello,

I like to draw dungeon maps and I recently saw a cool effect that I'd like to replicate. The effect makes it so that you can automagically easily draw dungeon corridors along with a cross-hatching pattern around them. The video below showcases this process.



The author of the video mentions using "custom hand-drawn tiling patterns", but I couldn't figure out what he meant by that. I tried creating a brush consisting of a square surrounded by a cross-hatching pattern but when I tried drawing with it it just kept drawing the same shape over itself, sort of like in the picture below.



I tried fiddling with the brush settings but I didn't find anything relevant. I also couldn't find anything on the forums here, though that might be because I am not sure what the exact query pattern might be to find this kind of thing.

Anyone have any idea how one would go about implementing this effect?