The method is used to combine two discs that were originally a single disc. So it all depends on whether your iso files came from the same disc. If they do, then you can simply mount the images and copy the files into the hard disc and follow the step accordingly. If they were iso files from different discs then it will be different because they will have different menus, etc. So DVD Remake will be a better choice for that though theorically you can merge them yourself with PgcEdit but it requires a better skill.