[Kreuger]

Before getting too detailed about armies and points, it might be worth considering exactly what you want to teach him.

I work in education and training. First you want to write a few learning objectives and pick the forces based on that.

I don't know how capable he is, so I'd probably start with 2 units per side with no cover. Then work my way up adding cover, new weapon types, new special rules, new scenarios, etc. and building up the complexity.

He will need to be able to consider all of these different factors and variables before he can compete effectively.

 

[Kreuger]

In training we refer to the ABCD's of learning objectives.

Audience - who. E.g. your friend, a 40k beginner.
Behavior - the specific action the trainee needs to complete successfully. E.g. selecting the right target during the shooting phase
Condition - the context for the behavior. E.g. each shooting phase when selecting targets
Degree - the quantity or quality which determines if the behavior is successful. E.g. selected the most appropriate target with 80% accuracy

I'm not sure how you say all that in Italian. =)