Adding it to your DX80 will increase only flash exposure. To increase ev at the camera you need to increase with the compensation setting on the D100.
Rather than blindly going with what you hear I would recommend that you be guided by what you see with the camera histogram. If you are seeing what you determine to be underexposure then by all means see what compensation will do for you.
The best advice I have found for exposure with digital is to expose for highlights and let shadows fall where they may. You can recover shadows quite nicely in post processing but blown highlights are gone forever.
I have a D1X but these principles hold for any camera. The histogram is an invaluable tool that I consistantly rely on to evaluate exposure. It saves my butt constantly. With film I almost always bracketed my exposures. With digital I practically never bracket. If the histogram looks good and there are no important blown highlights I go to the next shot with confidence.