Draw (or depending on the child’s developmental skills, have the child trace or independently draw) a large rectangle on the paper bag (use the blank side if the paper bag has a design or picture on it) and ask the child to cut it out.
Fill the squirt bottle with water and have the child spray water all over the cut out rectangle. Encourage the child to utilize his thumb, index finger, and middle finger to press on the handle of the squirt bottle. Once the paper is moist, ask the child to use both hands and squeeze the paper into a little ball (have him squeeze as much as possible and drain out as much liquid as possible).
Then, ask the child to open up the paper and use both hands to flatten the paper back to a rectangle shape.
Allow the paper to dry up before you start drawing or painting on it. For a rough texture, let the paper dry on a flat surface in the sun. For a smoother texture, you can place the paper between to flat heavy objects.
Once the paper is dry, have the child use markers to draw the outline of the desired picture and use the paint to paint it. To work on pre-writing skills, you can outline lines and/or letters and have the child paint them.
To promote sensory processing and tactile perception, you can have the child use the paper with a rough texture and paint with finger paint.