I have a Canon Pixma MP250 now. Previously I had a Lexmark X-74. Both All-in-Ones with two cartridges.
I filled the Lexmark many times. A Tesco refill kit came with syringe and instructions including my Lexmark (ie where to drill the holes in the cartridge)
Technique for Lexmark. Fill till the ink just reaches the hole. Wipe excess. Stick some tape over the hole.
My new canon decided to piss ink everywhere when I did the same (black cartridge. Not filled colour. I hardly use colour).
An online guide said 9ml capacity, but I only got about 7ml in to the top.
Wiped and taped. But it just kept oozing and oozing through the head.
I syringed 3 ml back out, and after a dozen prints and cleaning the head with kitchen roll, it started behaving.
Found my instructions for the cartridge somewhere online. Google canon catridge refill instructions or something.
Syringes and needles available at any pharmacist.
Don't worry they don't assume you are a druggie.