Dip pens are great fun because 1) dip pen nibs give you lots of lovely line variation. 2) You can use any kind of ink you like - from permanent indian ink to acrylic inks. 3) Their replaceable nibs are inexpensive. 4) They are low maintenance.
Here is a video demonstration of the process:
But most people say they are troublesome to carry out of the house because, unlike modern pens, dip nibs require you to dip into a bottle of ink every now and then. And that can easily result in spilling/dripping ink all over a cafe table or all over your nice clothes.
So here is my solution:
I found these squeeze bottles from a female cosmetics store in Singapore (Sasa). They have a cap, a nozzle you can pull out, and they are soft. Also very very light, compared to ink bottles made of glass. You can search for the same exact bottles. Or perhaps something similar.
I use a syringe to fill them with ink. (Winsor and Newton, Talens Drawing ink, food colouring.)
A needle with a large hole really helps, by the way.
The good thing about these bottles is that they won't spill ink, even if you turn them upside down. Ink only comes out when you give a squeeze. Because the bottles are small, you can control the flow very well.
When I'm on an urban sketching outing, or when drawing at a cafe, I simply squeeze some ink onto the underside of the nib. (I'm using a G-nib here.) Then I start drawing.
I don't have to worry if the bottle is upright or tilted. It feels a lot neater and manageable than with a glass bottle of ink. I guess the main things is that, I don't have to worry about holding the bottle at just the right angle. It can roll around on the floor and it won't spill.
I've even tried drawing like this at the backseat of a moving car and there were no spills. So long as I didn't add too much ink to the nib during each squeeze, it was fine.
Hope this encourages you to use dip pens more. They are fun!
P.S. This can apply to brushes too.