Yesterday I received a parcel with three new bottles of black ink. It is waterproof and it has plenty of colours, probably not as much as Noodler's but they are really nice and quite safe from impurities. This is the reason I have decided to use it in my brushes.
I refill my fountain pens and brushes cartridges with a syringe. It is preferable that you use one for each colour if you do not want to pollute brighter colours with darkest.
Here it is an sample with blue grey ink. I have refilled five brushes with blue, green, red, a mixed of blue and red and finally with black ink.
Here it is a detail from the drawing from above. I love how ink behaves, it is like watercolour. It is also important which paper do you use. Here I have used a Leuchturm 1917 sketchbook. It is not suitable for wet media but it stands the use of ink as you can see.