Here is a very simple diagram to show how to add a TIU in passive mode to see if it will work without too much rewiring. I'm not sure how your TMCC layout is wired, but I'm assuming you have added power drops off of a bus around the layout to maintain voltage. Ignore the SPST switch; I forgot to delete it for this discussion.
If this does not work, and again assuming you added power drops off of a bus, you can cut the wires at the bus and run them back to a terminal block. Cut the center rail halfway between the drops and now you have blocks.
Again, there are other factors that play into this like how many track sections per block and how many blocks per TIU channel. Enjoy.
