Right metering mode to use?

I'm wondering what type of metering to use for longboard photography?
I have a nikon d5000 and want to start photographing my brother doing longboarding and skateboarding. I will drop the exposure by about 2 stops and then fill in his body with a soft flash. I was wondering if:
1: this will work and 2: whether the metering mode matters and if it does then what type of metering should I use?

There's NO right metering mode. That is why there are so many choices. It is up to the photographer to determine that and knowing which to use only comes with experience.

When I'm shooting with a super wide angle lens I use the spot meter mode. Other wise I use the center weighted mode because that is the mode I have been using for decades and I know exactly how to meter with it

The best thing to do is take a reading by any means that you wish. Take a few test shots using MANUAL MODE. Look at the results in the monitor. Make sure that you don't have any blown highlights. Use the "Highlights" mode on the LCD to see this easily or check the histogram to be sure that it is not stacked up against the right border. Add the "soft flash" and see how it works out for you. Zoom in and look at your brother's face to see that it has adequate exposure. Once you find a setting that works, it will probably work for the rest of the shoot.

Is this how I would do it? No, not really, but I can't talk about choosing a Zone V tone without knowing more about your experience. Try it the way I described and it will work out fine for you.