As I understand it the method is about thirty years old. In the morning you get up and put the child in underwear for the first time-making a big deal of doing so. Ideally the days before you will have been showing the child how the toilet works, and have been putting a doll on the potty after pretending to have the doll drink. You may read books on potty training, or watch DVDs too.
Then you offer the child lots of an enticing drink on the potty training day. Taking the child to the potty ever half hour-an expect lots of accidents. Ideally this should be done somewhere without carpet
If the child pees on the potty, then great, put a sticker on a chart. If they don't, drink some more soda and try again half an hour later.
If they have an accident, don't make a big deal of it. Move them to the potty whilst they are peeing still, don't remove underwear but try and catch some pee in the potty. Clean up the floor and them-warm weather is best for this.
This relies on having the child drink more than normal to present more opportunities for learning. The problem would come if you never have a catch in the potty because you never have the chance for positive reinforcement.
As for trauma-it all depends on how the parent deals with it.