A "pressure washer" uses an electric motor (or gas) to increase the pressure. Usually pressure washers start at 1,000 psi for inexpensive ones and go up to 5,000 psi for industrial or agricultural applications.
The cheaper units are usually only good for intermittent use. If you try to use them every day, you might only get 6 months out of it. The larger ones will last a year or so and the industrial ones will last for many years. "You get what you pay for"
Without a pressure washer, you are only spraying the static pressure in your water supply. Usually 60-80 psi for city supplied water and 40-60 psi for well supplied water.
No matter what nozzle you use, you can NOT increase pressure, contrary to misleading advertising claims. Certain pinpoint nozzles only increase velocity, which doesn't help with this problem.
I can tell by the pictures, you have other issues too. One is: DO NOT ALLOW THE RECLAIMER TO DRY ON THE SCREENS !!!!!!
This will "lock them up" and then you need a pressure washer AND other chemicals to soften the emulsion.
Underexposure will also allow the emulsion to get "locked up". If your using a pure photopolymer type emulsion, you can NOT post expose screens. They must be completely exposed during the initial exposure.
DO NOT USE Lacquer Thinner, Paint Thinner or Acetone to clean off the ink. All of those solvents will "lock up" most emulsions that don't have a high solvent resistance. Use any of the more expensive Eco-friendly ink removers.
With proper exposure and completely removing ink with the correct type of cleaner, the emulsion will literally "fall off" the mesh without the need for a pressure washer.