I don't own a microwave...how would you reheat plain cous cous?
I would wrap in a lightweight muslin or cheesecloth and steam it. Or heat in a low oven, wrapped or covered.
A double boiler is another option, or you could try tossing it in a skillet, fried rice style.
add a little water to it and cook it over the stove under low heat.
Toss it into a sieve, set over a pot of boiling water (or broth) and cover with a lid.