I've had good success with DTI in the past though I don't do it often. This method is somewhat hit-and-miss. Sometimes the results are very good and other times I barely notice them. For protecting against negative side-effects it is best to pick a model that you would not mind being like in areas other than the skill you with to model.
The way I did DTI with great success was with martial arts training. I was in a car accident and was out of training for about a year when a friend who teaches martial arts wanted me to do a demo with him. This was going to be at a large church picknick with hundreds of spectators. I took a video of my instructor that I thought would be impressive. My instructor at the time was a very good fighter. I put the tape in my VCR, went into the accelerated learning state, and stated as my intention to model his skills. I watched the video in the state and when it was finished I put myself in trance. I told my unconscious to bring up everything I learned from him in person as well as on the video. I then used the DTI process from "Training Trances." I met my friend the day before the demo and he was impressed but he said that my style was too aggressive and he wanted to do a demo on a softer style called Togakure Ryu. I've never studied any specifics from that style and it really made no sense to me. I did have a video from the Grandmaster Masaaki Hatsumi (available from www.ninjutsu.com) and I did the same with that that I did with the other video. The next day I went to the demo and it went very well. I did techniques I never learned (or did not know I learned 
) and people came up to use and said our demo was "awesome." A few months later I watched the video again and saw the techniques I used in the demo. I never had success anywhere near that level since then. When I was in a hypnosis class I asked the instructor about it and he said that my intent for learning the skills to do a demo is much stronger than my intent to do it just for the sake of improving my skills. Having a good, immediate reason to learn whatever skills you wish to learn is important IMO.
For the most part I prefer the New Behavior Generator, whether doing it just in my mind, or even better, projecting the visualization out into the real world and moving with it. When doing it just in your mind, make sure to use other modalities other than just visual especially if it is something like martial arts or sports. For those you will need to add in kinesetic as well. My results were not very good when I only used the visual modality. It is just like in Imagestreaming. Use all of your senses.
When choosing between DTI and NBG, what i do is use DTI if I want to model someone on a more global scale and the NBG when I want something specific. I have found that it works to give your unconscious the instructions to only try on the behaviors, values, beliefs, and attitudes for a specific time period to see if you like them. Be careful with using DTI when modeling people with physical problems like diseases, allergies, addictions or being overweight. Many people who modeled a very skilled NLPer have gained gotten fat like him. I gained 40 lbs in 4 years after modeling an overweight martial artist/NLPer who also modeled this guy. I actually did multiple sessions because I really wanted the skills. When doing DTI, only model people who are fit and healthy, both mentally and physically. NBG is much more specific on what it models and so is much safer.
On a similar subject, avoid deep rapport with people with any mental problems. Rapport is similar to modeling. I know people who were getting wierd, paranoid thoughts when being around paranoid people and getting into rapport with them. this is one reason therapists sometimes have mental problems of their own.
