Ian: If you only need to hang a pair of doors and want to avoid using a router, you could use this tool. It comes in different sizes. After marking the hinge locations place the tool on the layout marks and strike with a hammer. The sharp edges will cut into the door precisely, then just use a sharp chisel to remove the waste to the thickness of the hinge.
Attachment 63342
To avoid measuring mistakes, make a measuring stick (3/4"x 3/4")the height or measurement from the floor to the underside of the top jamb, use this to layout the hinge locations and transfer to doors, it is critical to keep the story pole 1/8" above the top of the door to keep the top of the door 1/8" lower than the jamb.