The thing that’s going to let you meet your deadline … or not … really is: “how you approach the project itself.”
Immediately disavow yourself of the notion that you will ever run (or submit) “a single render job” which, by itself and with no post-processing, produce (“tah-dahhhh!!”): The Complete Shot.™
Instead, what you need to plan to do is … to plan. Break the shot down into constituent visual parts that will eventually be composited together. This is exactly like the “multi-track recording” process that is used to make every recording that you hear on the radio, and for exactly the same reasons.
Once you have a particular visual component, “isolated and pristine” and saved into its own MultiLayer OpenEXR(!) file, you can begin to build-up the shot in a “mix-down” process, exactly like they [used to …] do with those massively-wide control panels in recording studios. You can tweak the shot-in-progress in real time, and decide what needs to be done next. The goal is not to have to re-render anything.
Start with an OpenGL quick-render of the entire sequence. This will exactly correspond to the finished shot … and, oh by the by, that OpenGL output (or, rather, other OpenGL outputs …) can often be used as part of “the finished shot.” No one gets to change the film after the final picture-lock. Nothing’s gonna get rendered except the exact frames that the previz indicates are required.
What you absolutely cannot tolerate is … what most people do attempt. Namely, “I’ve got to spend a day-and-a-half (or more) rendering this, and, if it’s not exactly right, I’ve no choice but to spend another day-and-a-half, and another and another and another.” You need to, first of all, start with an approved previz-shot, and then systematically move, sub-render by sub-render, “mixing-down all the way,” until you arrive at the point where you choose to say, “okay, that’s good enough. Shrink-wrap it and ship it.”
And, “oh Lord, cheat the hell out of every shot!” :yes: Come up with at least two other ways to do any computationally-expensive stuff, like fire-and-smoke, and be sure in any case to wind up with a compositeable layer consisting (say …) “only the fire, no smoke,” and, say, “only the smoke, no fire,” and, say, “only a distortion-mask that suggests the presence of heat.” When faced with any obstacle, step back and say, “well, how else could we do that … just good enough?” If Star Wars Episode One shipped to theaters with a podracer-crowd that actually consisted of colored Q-tips cotton swabs, so can you.