Hello everyone! My name is Aspen, @Paraslider on Twitter, I'm an artist and animator entering college this year, and I'd like to say I've been using these for 2 years now and they still work fine to this day. Some problems arose with the paint itself, which I'll get into later.
For now, I'll start off with a brief introduction to how these pens work. Posca pens are notable for their usage in graffiti and street art, so the pen nibs are pretty much made to go through the wringer. As long as the surface you're going on isn't *too* toothy, like a broken brick or something, you can expect the nib to last a while. That being said; if you plan to use these on any kind of paper, expect the paper to pill. Pilling is the result of the pen nib being so abrasive on the paper's surface that it rips up the paper's surface/tooth. It won't destroy the paper by any means if it's watercolor paper or heavier weight paper, but printer paper is never ideal for these. The way you activate these is fairly simple-- you just press the nib down on a surface a bunch until the paint fills the nib, alternating between shaking the pen (cap on, of course) and pumping the nib like crazy until you get a nice, clean, consistent stroke.
Let it be known, though, you will be shaking these pens a lot. I don't want to understate this in the slightest. You will spend a lot of time shaking these pens. If your batch is particularly fussy, hours even. When I tell you I've spent upwards of an hour or two just shaking and pumping my pens for the second piece of art in particular, please believe me there. Once that's done, you should be smoothly sailing. If not, I can only refer you to Kasey Golden's posca pen videos on YouTube for troubleshooting and tips.
For clarity, I'll describe the processes behind each of these art pieces, as the size you're working on and the surface material matters greatly.
1- The first painting (the side profile of my OC, grey background) is something I was able to do with just this 15 pen set, and it was my first go with these, done around late 2018. Watercolor paper, 7x7 inch size if I remember correctly, and yes, the paper pilled here and there. It wasn't at all a distraction or a major flaw of the markers, and it turned out perfectly fine. It sort of feels like eraser shavings, and if you like the texture the pilling produces, feel free to keep it! if not, it's really easy to wipe off after the paint dries.
As can be seen, with just the base 15 markers, a lot can be done. If you're looking for a challenge and can work in a limited color palette, this set can take you far. The colors dry opaque and are super vibrant as expected. The coverage, especially for 3M size, is really nice and it dries down smooth and matte, no streaks abound. Poscas are renowned for their ability to create flat, sleek color blocks, so if that's your thing, you'll love these.
2- This next piece (pattern background, 4 characters) was a lot larger than the first one, and was done on a 16x20 inch canvas and it was completed around a month or two ago. It's clear that I expanded the color count here, and you can totally buy different colors of posca pens on amazon for relatively cheap if you get them in packs. Individual pens, however, tend to be a lot pricier and more of a hassle to get, like 6-10 bucks a pop. Unlike the paper, there was no pilling at all on a canvas surface and was overall a much smoother experience. It took a bit of getting used to the canvas's surface, but it was a really fun project regardless.
Aside from all the troubleshooting I had to do.
You see, herein lies my major point of contention with these paint pens, but I'm sure this isn't just limited to posca, but all paint pens in general. I was painting this on an angle, and the canvas was stationed on an easel. Because of gravity, you can expect some of your pens to go rogue on you. They may appear to dry out or get streaky, but this is just due to the orientation of your canvas. This can typically be fixed by pumping the nib and shaking, but I will admit even after a while of this, some pens just don't want to cooperate. Some might stay watery, and others might stay streaky, and some might just die on you, and that's when I suggest a replacement. For instance, the navy blue and regular blue colors here were really temperamental, but after some deep, mindful, therapeutic thoughts such as "goddamnit, please let me finish this before these die on me" I was able to power through. Don't give up on your pens because they're showing signs of wear, because there's a chance they might still work/can be revived.
TL:DR; These pens are spectacular for any artist of any skill level, but they aren't perfect and have some flaws. The orientation of the pen and your canvas affects the flow of the paint. In general, you won't see these problems with a majority of your pens, but every once in a while this may occur to a few in your batch. These are lovely for color laydown and produce consistent vibrant hues. They are definitely an investment though, so consider how you intend to use them and if it's worth the cost. These will make a lovely gift for any artist or creative!