Hello there,
If in the aircraft, you can look at the number at the bottom of the DI before you make the course reversal and turn onto that.
Assuming your DI is working and correctly aligned of course.
Or in the classroom, similar to the +200 -2 thing:
If heading is less than 180, add 180. Less is more
If heading is more than 180, take away 180. More is Less
Whichever method works best.
FIF