Your on the right path. Even though it may be bundled in with other wires, making a haness, the turn signals are their own circuit - depending on the year it will include the parking and brake light circuits. Just copy what they did originally. aside I never understand why people suggest modifying and 'improving' to folks who are already delving into new area they are unfamiliar with. Make it like the factory, it will work good as new. Mods can follow if wanted, but at least there is a good working system as a baseline.