I always wanted a nice t shirt with the millennium falcon on it, but unfortunately never found a fitting, pretty womens shirt for a reasonable price to just buy myself one, so i gave it a shot to make one my own with a cheap but nice plain t-shirt and a black textile marker.
I first used a how to draw the millennium falcon tutorial (linked) and practised a bit on paper, than tried it on the tshirt with a washable marker, and redid the good lines with a non washable black textile marker.
doing this with a marker is easiest, and gives it a cheap amateurish feeling that you can either love or hate. I like it myself.
make sure you have the shirt stretched around a big book or something for the lines to come out right enough, and when you got the outlines of the falcon right, you really can'r screw up the detail lines.