Any tips for lefties? I find in very difficult to avoid complete smudgification of everything I write with a fountain pen, since it takes so much longer for the ink to dry.

What I’ve seen being done before, not only by lefties but actually by quite a few people, is to shift your paper 45~90°, so that you’re effectively writing bottom up (right handed) or top to bottom (left handed). It can get a moment to get used to it but it alleviates the smudging significantly.

For what it’s worth, personally, I don’t like it so much, but I know people who swear by it; and had fast, clear, legible notes to back it up.

I write with my hand below the line to avoid smudging. A consequence of this is my pen meets the page at quite a shallow angle which I find is perfect for fountain pens but scratchy with ball points. These days I do very little hand writing and find my traditional pose (described above) causes hand cramps, but I don't know if that's specific to the odd way I write or if all poses would when so out of practice

I recommend using a sheet of tissue, napkin or old school blotting paper under your writing hand.

This advice is not just for lefties. Although I'm right-handed myself, I like to use a tissue paper under my palm when scribing Wedding Cards, to avoid smudges.

Try writing right to left!

Try different inks.