I did this procedure at home to my wife.
Her ear was blocked by a black compilation of ear wax. Instead of syringe, I used this.

I can fill more liquid with it compared to a syringe.
For the water, use warm water that is close to body temperature. It helps to soak and moisten the compacted earwax.
Took about 20 refills to finally dislodge the ear wax. It looks damn disgusting, but really satisfying when the big goo comes out. But at least it there is minimal risk using water to 'waterjet' the earwax.