As a lefty, the ink's drying speed is key, but also, the size and shape of the nib. Lefties should be using big bulbous bold 1.0+ tip nibs that glide across the page instead of stab into it.

Unlike a rolling ball pen, it won't skip or fail to roll with pressure due to the rightward angle-of-attack against the paper, so a proper fountain pen is actually better than most other pens for us lefties. First time experiencing smooth writing in my life.

Ultimately, the enemy of lefties is the pointy tip, and the rolling ball that's expected to be rolled against the paper, not pushed against it. Felt-tip pens work just fine for us, so those pen Sharpies are alright, but so are the 1.0 bold tip roller ball pens from Pilot, at least all the Pilots I've tried. Can't say all the others work as well.

Fellow lefty, fountain pen user. Just my 2 cents if any other lefty reads this and takes the bold nib advice at face value:

Although I prefer bold nibs, and the reasoning of your comment is sound (bold is going to be smoother and easier to push, which is what lefties do on paper), you can definitely get away easily with medium nibs too as a lefty, unless they are badly tuned.

Fine and extra fine sized nib are a matter of 1. taste in smoothness and line size, 2. how well tuned they are, and 3. hand writing position:

I don't enjoy particularly the fine line they leave, but I have at least an extra fine (european, on a Diplomat Aero) that writes really well, and it has very little feedback when sliding on paper, to the point it's almost smooth (I prefer smooth over feedbacky) even left handed.

There are cheaper pens on the market to try out different nib sizes, if one enjoys pens like I do, definitely find your favorite

And these are the most common nib options, there's even more :)

A friend of mine, a lefty, built a little writing table with a surface warmed by a small heating pad to dry his fountain pen ink rapidly. He used a smooth, rubber-like, or maybe vinyl, drafting table mat to cover the writing surface. It worked for him. I thought it was ingenious.

You could also use a Noodler's "bulletproof" ink on cheap paper. The cheap paper will have lots of exposed cellulose, and the bulletproof ink is designed to react to and bond with cellulose. A lefty will smear Noodler's bulletproof inks on high-quality paper designed for fountain pens and calligraphy, because the sizing (coating on the paper) keeps the ink and paper apart (for beauty), but on cheapo printer paper, it bonds (like ballpoint pen ink, it doesn't dry, it polymerizes and bonds) almost immediately.

Interesting. I use Noodler's Bulletproof for check writing due to its alleged strong resistance to erasure and check washing. I have seen it mentioned as being well-suited for use on cheaper, rougher paper but hadn't really given it much thought and it makes sense that it'd work well for lefties.

That's pretty clever! A good writing surface other than a wood table can also improve the comfort of writing as well.

Two other pens you might want to look at/for are the Platinum Preppy (a very cheap clear plastic pen, intended to be disposable but which can be eye-droppered or used with a converter/cartridge) and the Pilot Metropolitan (a metal body with a cartridge or converter, about the same price as the Kaweco Sport; I found one once at a Walmart). Both tend to write very well.

My pocket-pen is a Pilot Petit 1, another disposable that can be refilled and dirt cheap.

Fountain pen ink does make a difference, but nib quality is probably the major factor.

I use an inexpensive Pilot fountain pen and it's awesome - solid, writes well. Uses any ink I put in it but I've definitely spent more time trying out inks rather than pens.

I love my Plaisir too! I have a green color and of course, it's always inked with green :)