I would recommend Rachel use simple sentences and compound sentences to effectively communicate her message to her younger brother.
Simple sentences are easy to understand and follow, making them ideal for explaining tasks to someone who may be unfamiliar with them. For example, "First, fill the bucket with water."
Compound sentences can help connect multiple steps or ideas together in a clear and organized manner. For example, "Next, add soap to the water, and then use a sponge to scrub the dishes."
By using a combination of simple and compound sentences, Rachel can break down the task step by step while also connecting related actions or concepts. This will help her brother easily grasp the instructions and successfully complete the household task.