Sir ... I feel for you, and can sympathize with you in many ways. I know what it is like to be alone with a blood relation when he dies.
Back in 1992 I was with my grandpa in a huge mall. We had just gone to lunch together and I realized for the very first time what a wonderful man he was and what a wealth of mature reflection and experience he carried with him.
As we were leaving the mall he asked me to stop for a minute so he could sit down. He did ... and then slumped onto the table and turned bright red. He had had a heart attack.... I went into complete shock. Fortunately I was able to have someone get some medics on the scene quickly. I was the last among the living to talk with him while he was conscious.
I tell you the truth when I say that I was numb inside for weeks. I not "comfortably numb" either. It was a dull, constant, throbbing pain. It took me a very long time to come to terms with it. There were many things I did ... but I take things like that very strongly to heart....
Don't try to "force" the natural healing process, but don't be inactive and just "expect things to happen" either. Remembering and going over your grandfathers kindnesses to you is an excellent way to begin. Speaking with others who also loved him about these things is also good. In other words, DO things to address the issue, but do not force it or expect it to work by a particular clock or schedule.
For myself, I am religious and have a belief in the afterlife and that some things we do hear after a person has passed on can help them somewhat (as well as oneself through showing a practical love and a sort of "thankfulness" for all they have given you). Therefore I "accessed" these ... errr ... means as a way of helping myself come to terms with the grief and pain that came.
Elfforceelf, please pardon and forgive me if you do not have similiar beliefs. I am simply describing to you what helped and worked for me. If your beliefs are similiar then by all means utilize the "tools" they offer you.
My deepest sympathies good sir.... I remember well how painful it was for me. I hope and pray that you will be able to come to terms with the whole thing as you should and in the time that is best for you.