Perhaps the usual way.
Remove the heads and insert them into warm water, deep enough to cover the head jets but not the electric contacts. Keep there for 5 minutes, remove from the water and press gengly over a kitchen paper to absorbe the maximum water and ink from the head, you will see the...
Ok, my first refill on this unit. I use to refill some HPs and Cannons inkjet cartridges and color (toner) laser printers.
For this printer I used regular color ink that I use to buy to HPs and Canons.
The first thing, there is one instruction at the internet about refilling these...