Writing parts with multiple voices

Just a tip, not a rule (I break it myself sometimes).

That one (as well as most close score SATB ones) seems relativly easy:

1. Enter voice 1 in top staff
2. Copy the entire staff
3. Swap voice 1 and 2
4. Move the endire selection down by a 3rd
5. Paste
6. Now correct the pist ao fall voice 2 notes, and the (very) few cases where the rhyxtim is (slightly) different
7. Copy the entire staff
8. Paste to bottom staff
9. Down an octave
10. Correct the pitches (and rhythm) in both voices of bottom staff

To me that's the fastest and easiest method

If the parts are truly completely independent, and you're not a pianist or guitarist or choir singer so you don't find it natural to read and write multiple voices on a single staff, then indeed, entering them on separate and then imploding can be a quick way to get the job done. But this will only work for those simple cases where it really is two completely independent parts. At least as often, music will go back and forth between a single voice and two, sometimes even three, from measure to measure or even within a single measure. So you definitely need to be able to enter notes in multiple voices directly at times.

So again, if you are having some sort of problem entering notes in multiple voices directly, then in order to advise, we would need you to post the exact steps you are following, so we can show you where you are going wrong and what to do instead.

BTW, just as with voices, MuseScore never leaves note input mode without your explicit instruction to do so. Undo doesn't exit note input mode - unless, of course, you try to undo past the point of the notes you actually entered. Like, if the last thing you did before entering note input mode was adding a dynamic marking, then you go into note input mode to enter some notes, then you hit Undo enough times to undo every single note you entered, the next undo will remove the dynamic marking and you'll be back in normal mode.

BTW, the piece you show two voices oper staff throughout, completely consistently, no exceptions. There is not a single "chord" (in the MuseScore sense) in the entire piece - it's all multiple voices. So no use of Shift+letter name will ever produce anything like what you see. You need multiple voices for every single measure, even the first - assuming you actually want to reproduce that measure, not some other measure that sounds the same but is notated differently.

Entering the second measure is trivially simple:

1) select the (presumably empty) measure
2) N to enter note input mode (you will be in voice 1)
3) enter the voice 1 notes: 5 C 4 C B 6 A
4) move cursor back to beginning of measure (Ctrl+Left)
5) switch to voice 2 (Ctrl+Alt+2 or click the toolabr button)
6) enter the voice 2 notes: 5 A E 6 F

In a piece like this, I'd be more inclined to enter the whole thing, or at least maybe several bars at a time, in voice 2, then go back and enter voice 2, rather than one measure both voice, then the next both voices, etc. Too much switching voices and moving the cursor around for my taste.

Do note that in my example, reversing steps 4 & 5 won't work. After switching the voice 2, the cursor can only move within voice 2, and since there is nothing in voice 2 yet, the cursor won't be able to go anywhere in that voice. In this case, rather than do nothing, it will indeed switch to a voice that has notes, since you di ask it to move the cursor, and that's the only way to do it. So maybe that's the mistake you've been making - trying to move the cursor in a voice that has no notes.