Does the beer taste like diacetyl? If not, then you don't need to do a D rest at all. However it won't hurt either. For my lagers I typically raise temperature after the fermentation seems to be around 2/3 to 3/4 complete, then keep it there until fermentation is 100% complete. Typically this will take 3-4 days, but sometimes it will take weeks. Let the yeast be your guide. When the airlock stops bubbling, the krausen falls, and the beer begins to clear, then you can chill back down to do your lagering phase.Do you rack off the cake before or after?