Let's say I have a mired value of ten and I have a six and three filter to get me there. With a filter factor of 1.2 and 1.4 do I ADD or MULTIPLY the factors to get proper exposure?

When using a two color meter indoors (Gossen Profi color on an Ultra Pro) Where exactly do I point it? Directly at the light source? Person's face? Supposing there's natural light behind the subject from a window? Supposing there's natural light illuminating the subject and tungsten and Fluorescent?

Let's say I was in a hospital and wanted to take a portrait under the fluorescent light. Can I still use a two color meter for figuring out the NON-green color cast and add an FL-D?

Let's say I'm completely in the shade. Do I point the color meter just up into the tree, at the subjects face, or out into the light away from the subject.

The manual for using the Profi color doesn't really help with where to aim the thing in all situations.

Thanks for your help,