Screen Drawing Fluid is one of the essential components needed for screen printing and can be applied by brush directly to the screen to create the drawn image. It can be applied neat but will probably require some dilution with water in areas with finer detail.
Once dried, use removable screen block to cover the entire surface of the screen. After waiting again for it to dry you can spray cold water on to the screen to wash off the areas covered by the Drawing Fluid and leave a surface that can be used to make prints using water based ink.
All of the materials needed for screen printing are available from Hobbycraft, why not give it a try?
Daler Rowney System 3 Screen Drawing Fluid 75 ml