Refilling a brushpen isn't hard, but it does take a little patience and can be fairly messy. You need to save your empty cartridges (some people wash theirs out first and let them dry, I don't, and it doesnt seem to make a big difference in ink quality), and you need a good eyedropper if the bottle you use doesn't have one.
Step 1: Disassemble inkpen like you normally would.
|Put the dipper right to the cartridge opening. You need to be careful, because it'll bubble up and you won't be to fill the cartridge.|
|You can use the brush tip to pop the bubble and continue filling the cartridge.|