What kind of exposure is the best to use?

The best exposure unit to use is a point light source. It will give the most accurate reproduction of you positive. There are a lot of different types of point light sources in our industry that will work very well. As long as they are giving off the correct UV light. Make sure it is giving off a light spectrum between 350 nanometer and 420 Nanometers. The equipment manufacture should know and have these specifications. It is only the Ultra Violet energy that is exposing the emulsion. Some of the lamps will be called Metal Halide, or Mercury Vapor. Stay away from Pulsed Xenon and Halogen, they give off very little UV energy.