Refilling the original Brother LC-61 cartridge is not practical because of the design.
Listed here are the refill instructions for the Printer Filling Station after market LC61 cartridges.
The cartridges are located at the bottom of this page:
http://www.printerfillingstation.com/Ink_Refills/Brother/08B.htm
and refill like this.

1) Remove the cartridge when it is running low or out of ink.

2) Drill a small hole in the top of the cartridge.

3) Fill your syringe full of the proper ink. The cartridge will take approximately 12ml of ink.

4) Put the syringe needle into the drilled hole and Slowly inject ink until the cartridge is full again.

5) After the cartridge is full of ink, you can seal the drilled hole with a set screw or just leave it open, it will not make any difference in the print. If you do use the set screw be sure to screw it down flush with the top of the cartridge. There is a piece that will have to slide over the set screw when it is placed into the printer.

6) Replace the cartridge(s) and run 1 - 3 cleaning cycles as per printer instructions.
Or print the following pages:
http://www.refillinstructions.com/black.htm  for Black
http://www.refillinstructions.com/color.htm  for Color