Perfect Pour over coffee? Most people mistakenly think that the key to coffee flavor is grinding your own beans. I am not sure how this thought populated people's heads but many other folks tend to re-enforce this notion, which somehow keeps perpetuating this false notion. Coffee flavor comes from the oils in the coffee beans, and like all oil, coffee bean oil also goes rancid, and at rate much faster than many people realize. If coffee beans are not stored in a vacuum, air will turn coffee rancid after about five days, and actually you can begin to both taste and smell the difference three days after it is roasted. This is true (Listen up!) whether or not the coffee is ground or not. Coffee is at it's peak flavor and at its most complex between 18 to 24 hours after it is roasted, and much of the CO2 has been given off. After three days, it starts to flatten out, and at five days, it has lost a good deal of unique flovors.
You can do an experiment if you like, by simply smelling the roasted beans after 18 hours, and comparing it to the smell of the beans at five days. Try also scooping up a handful of the same beans and smelling the same newly roasted coffee to the (same variety) of beans that were roasted ten days earlier but stored in the open air. You will be amazed at how rancid the coffee smells. Unless you have experienced this test with your own nose, it will hard for you to understand why some higher end coffee shops have the ability to brew coffee with intense and complex delicate flavors. There is little mystery here. Your 5-10 day old roast may be freshly ground, but the grounds that result from that effort, are long past their prime.
Storing your coffee in the jar in your Fridge or in your freezer won't really preserve your coffee's freshness. You need to keep it in a vacuum (no air please). You can order a container that comes with a hand pump, and pump out the oxygen. Simply place he lid on the container, but the rubber stop on (similar to the one used on wine bottles, and using the hand pump, pump out the air. This will extend the life of your freshly roasted coffee well past the five day maximum, and keep it close to the freshness that it had at day one.
For years, I failed to understand that water temperature was also important. Having the water too hot or not hot enough will spoil your result. No reason to guess any longer. There are number of pour over kettles that either come with a gauge or can be outfitted with one. I used to boil the water and then estimate how long to wait before pouring. That is not a recipe for success. Buy the bloody gauge! It's important, and that way, you can learn for yourself how temperature affects flavor.
Use a quality paper filter if you don't have a gold filter. Note that the gold filter has to fit the shape of the metal or ceramic holder it goes into perfectly. Otherwise the flow rate is most often going to be incorrect. One of the most famous brands of filters no longer makes a gold insert that fits their famous long standing ceramic cone holder. Corporate blunder. Too bad. You might find one third party.
I think I can taste the fact that bleached paper has somewhat less of a paper taste, but I do wet the paper before hand pouring hot water through it. I also do the same if I am using a natural non-bleached paper or bamboo paper. There does seem to be less paper taste if I do. If you want to taste all of the complex additional flavors that come with fresh beans, you might also find that wetting the paper before putting the grounds in, and actually pouring some water through first does help. Why not experiment?
How long to let the coffee bloom before slowly pouring the rest your water through the grounds. Why not experiment with each variety of bean. The fineness of the grind is a factor to how long you should increase or decrease the bloom time. Generally speaking the courser your grind, the more time you will need to let it bloom. This is really the domain of experiementation. I don't increase the grind to get the shortest bloom time. I know some coffee shops do that. But I suggest experimentation. One to two minutes of bloom depending on your grind. But experiment, please.
The bottom line is the freshness of your bean. Good coffee roasters cost a lot of money. Air roasters start at about $200 these days, and good drum roaster that roasts 1/2 pound to 2 pounds can cost as much as $1500. That's a lot of money folks Does it make a huge difference in the flavor. Yes it does. It makes a huge difference to have fresh beans. In fact, it makes THE MOST difference provided you can store what you don't use that first day in a proper container. You can get your brew method completely right, but if your coffee is not fresh, it may be smooth tasting but it will always be missing the unique and complex flavor it could otherwise have. In short, smooth but flat as a pancake no matter what your technique, water temperature, or equipment.