Assuming you are starting with a commercially made dvd, you’ll need to decrypt and rip the movie to the hard drive, then copy over to the blank dvdr.
A free decryption program that is still being updated is DVDFab HD Decrypter. http://www.dvdfab.com/free.htm Be aware that as you use the free decryption section, you are using up the 30 day trial of the full version. The free part will still function after 30 days.
Once you have the video on the hard drive you may have to reduce the size with DVDShrink, but you seem to have experience with that.
Nero can burn your dvd video for you once it is the correct size.