Yep in photoshop draw a rectangle with the rectangle marquee tool (looks like a square made with dotted lines). Hold shift at the same time if you want it to be a square.
then edit>stroke
chose the pixel width- 50 or so
click on the color to change it
choose outside or center if you want rounded corners or inside if you wanted squared corners
HTH
otherwise like Dianne said- you will get the best response if you post in the forum of the program you are using.
BTW- usually brushes are used more for "stamping" images on your LO- like in rubberstamping
You can brush a straight line if you want a grungy looking line.
