[Big Ern]

First off, this is not the best or only way to light a map. But it is one way of doing it.

You can use ambient light. Basiclly, open up MOHradiant. Then press escape to make sure nothing is selected. Press "N" to bring up the entities window. Scroll down to worldspawn and select it. Now, in the Key: _____, type in ambientlight. In the Value:____, type 30 30 30 for dusk or 70 70 70 for day time.

Try that out, and see if it's what you were wanting.