The mechanics are simple adding -s, some minor variations according to spelling (box -> boxes, when to change -y to -ies), and a few exceptions (women, children, oxen).
I wouldn't try to cover all of the issues at once- if you threw one sheep/two sheep and cattle (plural verb, usually no number) at a beginner from a language with plural form, you might see their brain overheat. Especially if you threw in collective nouns with the differences between AmE and BrE.
Singular and plural is one of the most complex things in English grammar IMO, but getting learners started has never been much of a problem in my experience.