Phil,
You don't need to focus the light, you simply need to block it from getting to the paper. Even with a fluorescent unit, you can put cardboard over areas you wish to dodge, and even use wands with a little flag on the end in the same manner as is done with an enlarger.
Think of the negative in the contact print sandwich as the projected image from an enlarger. As long as you can see where the details are on the negative that you wish to dodge, you can block light from getting to them to affect the image in the exact same manner as an enlargement.
If you are talking about a digital negative, put the adjustments in the negative and print them straight.
---Michael