Make two or three large washes as a first layer, and let them run into each other on the page, so that their edges flow together somewhat. There is no need to correct anything. Whatever happens will be fine. The only requirement is that all of your washes and strokes be fluid and transparent.
While the washes are still wet, make a series of strokes with your biggest brush, so that each first-layer area gets a second layer of marks. If some of the washes are already dry, just carry on with the strokes anyway. Use as few or as many colors as you like.
Now make smaller marks that touch the big strokes. They can overlap as much or as little as seems right to you. Let the paper dry completely, so that it no longer feels cool to the touch. A hairdryer is useful.
Now mix up a puddle of a color that contrasts with one of your original washes, and lay it on top of part of the first wash. Leave some of the first layer unglazed, so you can still see the original color. Do the same for the other first-layer washes.
You might be tempted to "improve" your page by removing paint. Instead, consider making a second version, and bring them both to class.