Dryfiring is like watching paint dry, so even after buying Steve Anderson's book, you need to be creative and constantly change things. I'm only good for about 15-20 minutes a day and have been reasonbly dedicated for the last 3 months. You will need a timer not only for the dryfire but for checking results. When I first started a good 5 yard draw time was 1.20 secs, now, believe it or not the other day I broke into the .70 range, which for me is a tremendous improvement. Won't try to be that fast in competition but I feel great knowing my draw is .5 secs better than before.
Identify your weak areas and dryfire (being creative) to help improve them. Good Luck!