1) when you are putting your key through diffusion, you almost always want to flood it. When you spot it, you are putting out a narrow cone of hot light. When you flood it, you are sending out a much broader swatch of light. Ideally, you flood the light, then place the diffusion at a distance that the light fills the diffusion. You will actually get more intensity of light this way, than if you spot it in. With a softbox, again, flood it. If you bounce the light off a piece of foamcore, again, rotate towards flood until you fill the foamcore with the light.
2)The light meter you mention is a classic, analog meter. I doubt it will help you at this point. Once you get the look you want, you could, out of curiosity and or scientific enterprise, measure your key vs. your fill light. But you have no real need to do so. If you were shooting film, you’d need this or some other meter. I presume you are shooting video, and for that there is rarely a need. (I do occasionally use a meter on video shoots when I want to make sure, without needing to have a camera up, that I am correctly balancing all the lights.)
Rick Wise
director of photography
Oakland, CA
http://www.RickWiseDP.com
email: Rick@RickWiseDP.com