From the viewpoint of someone who works almost entirely by hand (by choice), you need a couple of things:
* a good bench with a flat surface, so that you can use the bench to check the flatness of pieces
* reasonably fast planes, and wood agreeable enough to use them
* understanding that before you get far in any piece of wood, you need to remove all of the high spots first. Sometimes, that's a hump in the back of a board, sometimes it's two tall corners, sometimes it's an area around a knot that is more dense. But no general attack will be useful if you start trying to plane an entire board when there are small spots that are high on it
* with choice of high spots, always remove the hump on the humped side of a cupped board first, it will relieve some of the tension in the board and the opposite side will be flatter.

I can generally create a board that is flat enough and square (edge to face) enough to need only minor adjustment before I ever pick up a square or straight edge.

Learn to use the cap iron on the penultimate and ultimate plane. It will significantly reduce your effort. In order to productively prepare stock, you need to be able to finish each board with through strokes from end to end and side to side, basically taking a uniform layer off.

Each time you plane, look at the wood you're planing and try to judge square and straight/flat before you check with tools. You'll develop a good eye very quickly, and work much faster.

I do have a thickness planer, but I have no jointer, and no band saw, etc. When I have to "haul" on a project, I will use a thickness planer after only jack planing a board. My jack plane is this one.
https://www.youtube.com/watch?v=2yYnjUhVvzk

(actually, I think I sold that one in exchange for a charity donation, but I have another one just like it). That plane is 17" long and can both remove material fast, and leave a medium hardwood flat enough in every dimension to go through a cheap dewalt thickness planer without getting stuck in the rollers - meaning, it's reasonably flat in length and with and planar. If it's not, a cheap planer can't feed it through continuously).

I prefer working entirely by hand, though.

Don't believe most of what you read on the internet, but do believe this:
* if you're going to work mostly by hand, find yourself woods that work well with it. Most people like to remind me that I know nothing about Australia, but I have worked woods up to kingwood and verawood. It's miserable to plane those - it's not even nice to *turn* verawood, the shavings sting you, they're so hard and brittle.
* most of the people showing a "method" to flatten and square wood don't actually do much (the wood and shop guy comes to mind, the performances look sort of credible, but they don't resemble someone who will work a few hundred board feet by hand).
* there is no single method. What you have to do is train yourself to remove material from where it needs to be removed, and then confirm the job is done with through shavings on the final piece. If you can't plane end to end and left to right, something is out of whack. You can still do that with uniform twist (but that's why you use your bench top to confirm there isn't any). Sometimes you have a narrow long board, sometimes you have a wide short board. Your approach to the actual heavy work will be different with either (you may plane across the grain with some, but not others).
* The conventional wisdom on the internet is that all heavy stock removal occurs across the grain. That's not true, and books like nicholson clearly state that work should be done with the grain when possible. There are times when that isn't optimal, but it usually is (it keeps more material moving through the plane faster for all but the coarsest work, or the short and wide type pieces). Heavy work should be done with the grain without a closely set cap except when needed. Penultimate and smoothing work should be done with a cap iron set about twice as far from an edge as the typical thickness shaving being taken.

And for the third time, the focus is getting continuous shaving through the plane. You can't get much done if you're skipping back and forth in an "X" pattern on a board that needs significant work, you're just mostly cutting ridges of the last cut off of your stock.

Run far away if anyone suggests that you should use a high angle plane for any part of this (including the smoothing - someone who uses power tools only and just smooths wood might need to rely on a high angle plane, but it will seriously impede your work and have you sharpening much more often).

As soon as any of your planes need you to lean on them to cut, sharpen them. You're increasing your fatigue level.

if you insist on using metal planes for pre-smoothing work, keep wax handy and wax more often than it feels like you need to. If you wait until you feel waxing, you're wasting energy. the fastest combination for rough work to a finished surface is a jack plane, a long plane with an aggressive cut (both wooden planes) and a stanley smoother (not an exotic smoother). If you work very soft woods, then a lighter coffin smoother may be as fast, but it won't be in hardwoods.

Nothing that can be planed can't be planed with a common stanley plane once you learn to use it. If you have a type of wood that is too hard/resistant to plane it with a wooden jack plane, then that's something you don't want to use. The wood plane is your canary as far as wood selection goes. I only used the exotics mentioned above for small projects, like infill planes. There are supposedly hard exotics, though, that do work really well with hand planes (indian rosewood, gabon ebony, etc, for different reasons - we don't need to get into them, but the planes will really help you understand wood characteristics much more than a table saw and sandpaper)