If you have time, try reading Closing Time, Joseph Heller’s hardly-ever-heard-of sequel to Catch 22; not in any way to try to emulate it, but to see how little plot matters. Catch 22 itself showed that side-lines can be as gripping as any real plot, and Closing Time does the same in spades.
At the end of the day, did the method you used for Book 1 work, or not? To the extent it worked, stick to it.
Who says outlining the plot makes things easier? Look, most obviously, at Game of Thrones and you should see that either Martin is at least as great a logician as a good writer, or he doesn’t bother with plot… he just sits at his desk and lets the story flood out, as much through as in any way due to him personally.
What is Book 2 about, please?
Is the whole thing about character, like James Bond or Jack Reacher, and all else is little more than an excuse for action, or are the books essentially episodes in a single story?
Either way, what’s the absolutely basic outline? “Boy meets girl” sounds too extreme for me but “there’s this character, who does that thing, which leads to this outcome…”
Then, what must be carried over from Book 1?
When you feel blocked, why not just ignore it and write on - quite literally? That is to say, decide how long you want to write for and in that time, write. When you feel blocked, write “block block block block…” or “write write write write” or any similar such nonsense. Use “Now is the time for all good men to come to the aid of the party” or “the quick brown fox jumps over the lazy dog” if you like, or swap them about. If you really have to, carry on like that for an hour or two, or six or twelve; the only point is to keep writing for the time you set yourself, with no breaks at all.
We don’t care how boring it is; when you do that you are writing, rather than worrying about not writing.
If you do that with plots or characters held somewhere in your mind, they will surface and start writing themselves.
If characters or actions surface first, fine. Write them up and save them for later.
If plot lines surface first, fine. Write them down and wait for their characters or actions to bubble up.