Early proponents of DCC touted the fact that you can hook up your railroad with just two wires. While this is technically correct, there are some issues that need clarification.
If you are wiring a new HO layout it is a good idea to use at least 12 gauge wire with feeders to EACH rail every 10 feet or so as a power bus. If you have an existing layout, the general rule is that if you can run regular DC engine around the layout, the wiring should be able to run DCC without problems.
Unless you need to section your layout for added power, the only gaps you need are for hard shorts such as reverse loops and un-insulated frogs. If you are already wired for block control, you probably don’t need to rewire to use DCC. Just open all your blocks so that the entire track has power and you are ready to go. If you are using common rail wiring and you wish to section your layout, you will need double gaps to separate the sections.
Remember, no matter how you control your trains, you should always use safe wiring practices.