Once a student can discern between her background parts and main melody parts I encourage her to use copy and paste as a way to fill out the orchestration. Going one step further - unison parts can be turned into harmony parts simply by moving them up or down 1 skip. For example:
What are your thoughts on this concept? Have you had any experiences with students using this in their piece?
If you have come across this topic note that it relates to the Harmony Module on the Music Works 1 collection here. Check it out for more info!