There's a lot of discussion about dip nib inks vs fountain pen inks. I think it's better to view your choices as one continuous spectrum from which you can choose the ink or paint you want to use.
With most pens, you have to decide whether to use a thicker or thinner ink and get the advantages and disadvantages provided by the type you pick. Dip nib ink is thicker and designed to flow over the surface of the nib, which is great if you're using a dip nib. It's not so great if you're using a fountain pen because the thicker ink can plug up fountain pens.
If you're using a fountain pen, the rule of thumb is to use fountain pen ink, which is thinner and designed for the narrow passageways in a fountain pen. You sacrifice color and density, but you retain the easy flow of ink through the pen.
Our pens let you use any type of ink or paint. If it flows, it will work in our pens. If you use lacquer or enamel, the flow will be very slow. You can use India ink and acrylic paint, which should flow very well. You don't have to worry about plugging up the pen, because our pens are made from a material to which nothing sticks. If the ink or paint dries out inside the pen and forms a plug, you can push it out easily. Just disassemble the pen and poke it out. You can remove the nib and feed and clean the front of the pen.
You might not want to bother cleaning your pen. You don't have to clean it every time you use it. You can set it down for a day, even a week, then pick it up and continue. The longer you let it sit, the gummier it will get, but sometimes that's not a problem.
Basic rule is that the cleaner you keep the pen, the better it works for you. But the type of ink or paint you use won't make a difference in the performance of the pen. You should feel free to use the ink or paint you want to use.