Well, there are a few things I can say regarding steel wool photography.
First of all, be safe! It's fire after all and steel burns at 1000 degrees Celsius.
The faster you can swing it the more air gets in, the hotter the fire, the more sparks you will get.
But practise your swing without any fire! It's better not to try and invent some new swing untested with shit that can burn you.
Next we never do this where there is a chance of things catching on fire. The ground around you will have glowing bits of metal; if there is something flammable it’s bound to catch.
Another thing is how every video seems to recommend the whisk as the tool of choice to hold the wool. Yes, it works, but the trouble is that once it burns down a bit, the chance of having chunks of what's left fly out increases. That flying ball of hot could mess up a friend, a camera or set something on fire. We found that a bit of rat wire wired on to the end of the whisk works well to prevent this from happening.
Oh and don't trust a keyring to hold a chain to your handle. The amount of centrifugal force straightened it right out, the flaming wool in the whisk went flying... ya, uncontrolled chaos.
Next consider your camera’s safety. It's better to use a zoom than to have the camera too close to the action. The sparks can fly quite far if you do it right. Alternatively, situate your camera almost directly at your feet as you swing, allowing the sparks to shower over the camera (and attaining a different angled shot). Do consider a lens filter as a way to protect your lens. A filter is considerably cheaper to replace should it catch a hot searing bit of ember. Again, to be on the safe side, do a dry run of the stunt minus the expensive camera equipment, friends, pets or anything else that might not take kindly to being charred.
Ok so you took all these safety ideas into account and you're ready to make it rain sparks. Have you ever wondered how to light steel wool? Lighting the wool can be a pain. It is metal after all. So maybe a 9-volt battery will work, but my cheap ones made barely a spark. A lighter can work, but you and the person waiting to press the shutter will have to have a lot of patience. Our preferred method - after a lot of misfires - is to use a sparkler, yes, the thing you played with as a kid works to get the wool burning really well. Just twist the wire handle of the sparkler to be sure it's secure and set the wool around it making sure the tip is out enough to get it lit.
So after you're done with the photo and just that teensy bit of glowing metal is left in the whisk... Careful how you knock it out! I banged the whisk on the blacktop and had a bit hit the top of my foot. OUCH! Quickly I took off my shoe to rub the spot and check if I was ok; my step back is what really got me as there was a hot ember lurking directly behind me! OUCH again!! So use caution. I can’t emphasize this enough.
Oh and a pocket-sized flashlight will really come in handy. Both for finding the spot you marked out so as to be far enough away from the camera but also to find your way back safely in the darkness. Remember that steel wool photography produces best results in the darkest of conditions, though you can do it in the ‘blue hour’ just after sunset. Safety first. Always. Good luck!