I do not subscribe to the start concept. When I added DCS when it first came out, I simply inserted the TIU into the wires from transformer to control panel. My layout was built for conventional, with some 75 toggled blocks on 6 "handles." 14 gauge wire goes from each toggle switch to each isolated block. Ground is by a 12 gauge buss that goes all around the layout. It works.
I strongly recommend you don't get chintzy on wire gauge. On an 8x4 16 gauge is fine, but on a larger layout, my experience is use 14-gauge.