Simple and inexpensive.

Because HP cartridges but are a bit expensive and I with the low cartridge the printer will not destroy,
I opted for the refill kit.
I've never done that. The instructions in the package is easy to understand. The only thing that is a bit inconvenient, is the poor print quality of the instruction. Therefore, you can see exactly where not to be the hole in the black cartridge.
But that can quickly find out by Dr. Google.

As a tip from my own experience I can say briefly that you have to watch what you are doing with the rod of the syringe. The should not pull too far, when the syringe is still full one. ;) I know that's logical, but can be the sometimes forgotten, since one is not reminded by a stopper in it. That would be my only suggestion.
And for the filling, the syringe should not be performed more than 2 cm in the sponge and you should really keep in mind the capacity slowly fill, so not too much in the cartridge, because then the color is simply running out the bottom.

In print all colors and black are very good and strong.

So and now a lot of fun when filling! If you have questions you can feel free to leave a comment.