A good first step here would be to make a list of the wetness problems that showed themselves in class yesterday. This works best when you are willing to take responsibility for both the successes and the failures. Saying, "The paper got too dry, so all the marks I made after that had hard edges" sounds like a form of pleading, "not guilty!" The fact is, it's all your job.
Generally speaking, wetness issues involve the relative wetness of the brush compared to the paper. When the paper is wet but the brush is wetter, blooms are likely. When the paper is dry all your strokes will have hard edges.
Nothing in nature looks more like a brushstroke than a cloud, but not every brushstroke looks cloud-like. Re-working your clouds to make them "better" usually accomplishes just the opposite. The sky is such a varied subject almost anything will work, as long as it looks like it happened by itself. Clarity and transparency. Weightlessness and insubstantiality. These are the qualities of a flawless watercolor sky.
For homework, please make as many sky studies as you have time for. Vary the colors, the values, the sizes, the edges. Let some of your shapes go off the page and some float inside the rectangle of paper. Experiment, don't correct. Work on wet paper and dry. Try wetting random portions of the page. Make some so wet the paint flows downhill when you tip the paper.
You can copy these, find your own, paint out the window or invent the cloudscape entirely. Have fun. Bring in everything!