You can do that with center or partial I am just wanting to know if he means setting it back to 0 when he meters on the other areas other then sky . I know you are trying to help but I was wanting an answer to this specific question please.
Short answer: No, you cannot, and no. Center-weighted and partial CANNOT be used to do multi-spot metering accurately. You're measuring too much stuff at once other than the shadow or highlight in most cases, and the meter reading is meaningless and misleading. You can't change exposure settings between meter readings or the results are meaningless. You have to keep the camera settings the same for both the highlight and shadow readings, or you have no basis for comparison.
Long answer: You're asking which hammer to pound screws with. Attempting spot metering techniques with center-weighted or partial metering is going to give inaccurate and misleading results, because your meter reading isn't going to be limited to the bright or dark area you're trying to measure. You're always going to be measuring other irrelevant stuff as well, and that will skew your readings to the point where thy won't be helpful. For the technique to give any kind of meaningful results, you have to have an actual spot meter, otherwise you're trying to do brain surgery with a chain saw.
I happen to have 2 top-of-the-line professional Canon 1-series DSLRs, and have shot nearly 150,000 frames between them. You know how often I use multi-spot metering? Never. Why? Because in the time it takes to wave the camera around and take enough spot meter readings to be sure I've measured the brightest highlights and darkest shadows accurately, I could have pressed the shutter release once, glanced at the histogram, made any necessary adjustment, and captured a few properly-exposed frames.
Your camera does NOT have the tool you need to use the technique you're asking about. Your meter readings will be wrong fairly often, and as a result you WILL have exposure errors. You WILL take longer futzing around with multiple meter readings than you would pressing the shutter release and glancing at the histogram. Since the histogram is an aggregation of several million extremely narrow and precise spot meter readings (one from each pixel in the sensor) not using it is one of the most foolish things you can do when shooting digital.
Basic histogram interpretation is easy. Look at the right edge. If there is a spike, you have overexposed. The size of the spike is an indication how much you've overexposed. If there is a gap between the data and the right edge, you have underexposed. The gap width is an indication of how much you've underexposed. Yes, there are some exceptions and caveats, but that's the basic concept. Start with that, and re-read my article as you get more comfortable with the technique.
You'll get more accurate exposures faster than with any other technique once you learn this.
