I suggest that we should decide right now while we are still alive, as to which Spiritual Guide, Yidam or Dharma Protector do we rely upon when we enter the state of death, instead of making a decision at that point. It's like choosing a guide in advance for a journey which we must embark on.
I do not know for certain how the state of death is really like. Different people offer different description as to how it will be like. There are many books by various authors on this subject. It's not like a place on earth where visit it, get a feel of the place, & plan our route when we want to revisit the place again.
I believe that each person's experience of death varies according to his karma; so to me, no two person can have the same experience.
Our choice of guide, which in this case, Dorje Shugden, is within our control. He will be like a life ring(ring buoy) which we hold onto in the possibly turbulent state of death.
Though this is crucial, I believe it is not everything.
What we must also do when we are in that state, is to make an effort to recollect the Buddha Dharma, and be in a state of mindfulness of it, because our future rebirth is dependent on this. If we focus on virtuous thoughts, our connection with Dorje Shugden will be stronger, and He will be more able to lead us to a better rebirth. If we focus on non-virtuous thoughts or total lose control over our thoughts, I believe it will be harder for Him to help us. So in this case, Dorje Shugden becomes a mnemonic aid.
Yet prior to all these, it is important to study the Dharma as much as possible while we are still alive, and endeavor to put them into practice to the best of our efforts, preferably bringing happiness to everyone around us, so that we can die with less regrets because we are satisfied with how we have used our time on earth, till we feel that there nothing more we can do other than what we have done.