I've received Dorje Gotrab from three different Lamas: ChNNR, Tulku Sang-ngak, and Lama Dawa Chodrak. All three transmissions have been based on Dorje Lingpa's terma and Mipham's commentary. However, each of these three Teachers has taught this practice quite differently.
ChNNR's transmission has been the simplest as has been explained already in this thread. Magnus's last explanation says everything that needs to be said from that POV. I have a long-time Dharma friend who did a three-day retreat based on this transmission and did see some sign of accomplishment. In his case, a ganglion cyst he had had for some time spontaneously remitted. I believe he reported this to Rinpoche Who did say this was a sign of accomplishment.
Tulku Sang-ngak in addition has taught the visualization and short sadhana by Khenpo Ngawang Palzang (a.k.a. Khenpo Ngakchung). Tulku Sang-ngak received this from H.H. Chatral Rinpoche (among others). So immensely great blessings there. When I received this practice from Tulku Sang-ngak I don't remember the idea of the silentthree-day retreat being stressed all that much. It was more as if the practice was being given as a short daily practice. However, given my age and failing memory, I may be completely mistaken about that.
Lama Dawa has received permission from H.H. Dungse Thinley Norbu to teach Dorje Gotrab as a complete path to Enlightenment. This is done through a series of retreats. The retreats are very strict, boundaried, and totally silent (except for the mantra). In fact, even speaking in one's dream is a breach of samaya which must be confessed and amended. At the end of each retreat, one is given a test (related to the various five elements) to see if one has accomplished the mantra at that level. One continues repeating the same level retreat until one manifests the correct result which is an observable change in so-called material reality. Some sadhakas progress faster and others slower. IOW, it may take an individual more or less retreats to accomplish a given level. Later on, the retreats are longer and eventually include yang-ti dark retreats. Between retreats, one must keep the samaya of saying at least one mala of the mantra each day. Of course, one can say more. While health and healing are major focuses of this practice, it obviously goes beyond those aims. These have been some of the most powerful experiences I have had in the Dharma in over more than four decades of practice. The way Lama Dawa teaches this practice, it is very unambiguous. You totally know whether you got it or not and what level you are on.
Although I feel blessed and fortunate to have received this practice from three different Teachers and Their respective lineages, IMHO, Lama Dawa's approach is in a class of its own. I highly, highly recommend it to anyone who would like to accomplish a Vajrayana practice and know
that they have accomplished it with all that that implies on outer, inner, secret, and most secret levels.
Typically, Lama Dawa offers Dorje Gotrab retreats each fall and spring. This fall will be the first series of retreats to be held on Rinpoche's land in Iowa. See www.saraswatibhawan.org
for more information.