Getting the Most From Scales

I feel that my students benefit by "overlearning" a few fundamental skills, rather than skimming or surveying lots of skills.  The question becomes, how can I keep the students engaged while repeating a fundamental skill like the 17 natural notes?  Here are some ideas:
---The most obvious is to vary the right hand picking or fingering.
---The next most obvious is to vary rhythm figures such as dotted quarter/eighth.
---Less obvious, but very interesting and "fun" is to play the scale in:
-------Contrary motion.
-------Parallel octaves.

Process:
---demonstrate the skill in repeated notes.
---echo the skill.
---play in unison.