First of all, I'm right-handed, so I don't really have any personal experience with the issues you left-handed have to face. Still, I've found myself helping more than one lefty with pen issues, so I might share a couple of the things I found out with them. Being left-handed doesn't mean you have to give up the opportunity of using less stressful writing instruments, be them fountain pens or rollerballs. Honestly, I don't think I could ever go back to a ballpoint keeping my current notetaking speed. Not to mention than after two hours of non stop writing with a ballpoint, my hand usually required a Gatorade bath to restart. All of this said, you might indeed have to consider the issue of ink smearing alongside the other problems that right-handed have to face too.
If you are a newcomer in the world of fountain pens, or if it's the first time you're trying to use them for everyday activities for which you previously used standard ballpoints, go dry. What I mean is: use a pen whose nib place it in the drier side of the fountain pen spectrum. As you might imagine, the finer the nib, the drier the line. Then, between nibs that write lines with the same size, there might still be some minor differences in wetness, usually due to the feed. As long as the pen isn't a flex one, doesn't have a very broad nib, or isn't known to be too wet, you shouldn't worry about the feed too much.
With a little more experience and practice, you might try stepping up on the nib size ladder a bit, if the size of your handwriting requires it. For instance, I started with a Fine and it is still my choice today, but I do happen to have a fairly small handwriting. Just remember that largers lines are wetter, and they will take longer to dry.
Specialty nibs are another kind of matter. Each type has pros and cons for left-handed use, so I'll try resuming them in sections.
- Italic nibs: they're just horizontally straight cut nibs, so the only issue you might have with them (that a right-handed wouldn't, I mean) is their wetness. Every pen with an Italic nib has a different grade of wetness, so there are those whose broader strokes dry quite fast, and other that leave a ton of ink on the paper. You might take particular care of the points where you stopped writing, because that's where you'll see the highest concentrations of ink. There are also "Cursive Italic" nibs, but they're rare to come by and they're just slightly rounded Italic nibs, so there shouldn't present any new issue.
- Stub nibs: they're basically Italic nibs rounded at the edges (more than Cursive Italics), to allow a larger range of optimal writing angles, which is usually the main issue with Italic nibs. They shouldn't present any issue that an Italic doesn't have.
- Oblique nibs: well, I think you might imagine the issue with them. They're oblique cut nibs, usually at around 15°, but they're specifically made for right-handed writers. Still, there are oblique nibs with a reverse cut, usually made for left-handed, that have basically the same issues of an Italic nib. Just watch out, as a nib that for a certain brand is "Right Oblique", might be a "Left Oblique" for another. Some brands with "Left" and "Right" indicate the direction of the cut, other ones use the terms to define which hand should be used to write with them.
- Flex nibs: that's another matter entirely. First, you need to be an underwriter to use the correctly, as an overwriter would end up flexing in the opposite direction. Still, if you're an underwriter, the only issue with them would once agin be the wetness of the broader strokes.
You might also want to mind the material the nib is made of. Steel nibs are stiff, unless they're specifically made to be flexible. 14 carats gold nibs are more springy, but that still depends on how the brand wanted that particular model of nib to be. 18 carats gold are usually made to be as stiff as steel, as the 18k is a much softer alloy of gold and it might be permanently damaged by continuous flexing. Brands like OMAS, for instance, offer both non-flex 18k and flexible 14k nibs on their high end pens. There are other nib materials, like palladium, titanium or chromium, which have unique properties, but are usually used only on particulary expensive pens.
Back to the issue at hand, I can't think of a better brand than Pilot for a left-handed writer. Japanese Fine nibs are finer than occidental Extra-Fine ones, and Pilot feeds usually do their job quite well.
Another thing you might want to consider is the ink. As long as we're talking about this kind of pens, you're usually bound to the ink you get, be it in a cartridge or inside the barrel of the pen. Pilot inks are particularly fluid, so they'll get absorbed by the paper in little time, reducing the risk of smearing. Still, the Metropolitan accepts Pilot converters, and you might really want to buy one at least for this pen. Put some fast drying ink in it and you're done! My personal suggestions would be any Noodler's Bernanke or Private Reserve Fast-Dry. I've also heard good things about Sailor Kiwa-Guro, which is why it is the top ink in my "to-get" list, but it happens to cost more than a Metropolitan...
Oh, one last thing. Paper. Rhodia, Clairefontaine and other smooth papers are certainly much better than normal one for fountain pens, but they do cause ink to be absorbed more slowly. Standard paper, on the other hand, absorbs ink faster but has an higher risk of feathering and bleed-through. With a Fine nib you should have less issues, but I would still suggest you, if possible, to try both kind of paper and see which one fits you most.
I hope I've been useful, and sorry for the length of my message!