Making whiskey is about more than just letting some grain ferment and drinking what's left over. If you want whiskey post-collapse, you better take note of what you will need to stockpile now. There's a lot of science involved, and learning the steps below will lead to a much purer product.

Step 1: Making the Whiskey Mash
Mashing refers to the hot water steeping process which activates malt enzymes and converts the grain starches into fermentable sugars. At this point you have a sugar rich solution called the ‘wort’ (pronounced ‘wert’). Yeast will convert the wort to alcohol.
Whiskey Recipes
Depending on the recipe you may need to transfer the wort to another container (fermenter) for fermentation. Once the mash has been prepared according to your selected recipe proceed to step 2.
Step 2: Fermentation
Fermentation: The biological process in which sugars such as glucose, fructose, and sucrose are converted into ethanol and carbon dioxide (CO2).
Once you have picked your recipe, made your wort and pitched the yeast the wort will start to ferment. This process can take anywhere from a few days to a week depending on the type of yeast, temperature of the ferment and nutrients available to the yeast.
Wait till you are not seeing any little bubbles being formed. You will see this at the top outer edge of the fermenter. If you are using an airlock wait till it stops bubbling and then give it one more day to rest. This is a rather crude way to determine the completion of fermentation.
Step 3: Distillation
Transfer to Still: Siphon or strain the fermented wort (aka ‘wash’) through cheese cloth into the still. The cheese cloth is only used to take separate the large solids. If you are siphoning the wash into the still try to leave behind the solids at the bottom of the fermenter.
Heat\Boil: Heat the wash slowly. The goal here is to not burn the wash. Give yourself 30-60 minutes to bring the wash to a boil. Usually a medium to medium high temp is adequate.
Start the Condenser: There should be a thermometer located just before the cooling condenser. When this reads 120º F- 140º F (50º C-60º C) start the cooling water for the condenser tube.
Heads Out: A steady drip should start to flow from the end of the condenser. For a 5 gallon wash throw out the first ¼ cup (~50 ml). This portion of the ferment is referred to as the heads. It contains methanol and some off flavors that you do not want in your final product.
Body In: Continue fermenting collecting the distillate in 500ml portions. This is the good stuff. The thermometer just before the condenser should read somewhere around 175º F-185º F (80º C-85º C).
Tails Out: When the thermometer start to climb to around 205º F (96º C) you are starting to distill out the tails (aka fusel oil).
Clean Up: Turn off or remove the heat source. Turn off the cooling water. Let everything cool and then clean thoroughly.
Step 4: Aging and Maturation
Whiskey is best when it has been aged for a period of time. Aging normally takes place in Oak barrels. However, you can also add oak chips to the whiskey and let age.
Step 5: Dilute and Bottle
In order to enjoy a glass of whiskey you need to cut it with water. Drinking spirits at 75%-80% ABV can be an uncomfortable experience. Generally whiskey is diluted to 40% ABV (80 Proof).

Knowing how to distil your own alcohols will probably make your life a whole lot easier when SHTF. You can either make it for your own use, or you can trade it for objects and services that you find more useful.

Essentially, once you become established as a local authority on the subject, you'll be held in much higher standing with survivors in your area and you'll likely be more protected as a result.

For more information on how to distil whiskey, check out How To Make Whiskey HQ.