What I love about these pens is the ability to work with my fingers to smear the paint. I find myself working very free and even working with both of my hands to get certain effects. I can also use a brush and a little water to spread and blend the paint, though I prefer the effect I get with my hands. If you want to see how cool these pens can be, check out the amazing surfboard artist Drew Brophy. He paints surfboards, motorcycles and helmets, guitars, skateboards, and more with Uni Posca paint pens. His work is very bright and bold and really speaks to me.
Here is a quick tutorial on how I am using these pens in my art journal. Following Drew's lead, I first make a basic outline with a pencil. Then I begin to fill in the various areas with multiple colors to get shaded effects (i.e. blue, light blue, and white in the flames). I shade the face in the same way shown in my 3-part "shading a face" tutorial on my Youtube channel. (Yup! You can shade a face with these pens. Just add the color a little bit at a time and smear it with your fingers. It works great!) The pens blend really well together and I can get great depth and shading. The last step is outlining in black and adding a few details and highlights with black and white. I also added a little glitter paint to the flames and the eye and lip.
One tip, you'll want to buy multiple black and white pens along with your color selection as you'll use these a lot for blending, outlining, shading, and highlighting. I bought mine at www.durablesupply.com. You can find them in numerous places on the web. I haven't seen them in any art/craft supply stores. Have you?
Have you tried Uni Posca paint pens? I would love to see what you are making with them.