Basic light-painting portrait technique used by pretty much everyone who does this: In a darkened room/environment, camera on tripod, light paint around the subject, then flash the subject at the end, all in one shot. Typical example:
The two main problems with compositing a light painted image with a subject image are:
1. The light from the light painting doesn't match with the light on the subject, so they don't look like they're actually in the light-painted environment together without a LOT of PS work on faux-lighting them. Viewer's brains know something's wrong, even when they can't quite figure out what the problem is. Light and shadow doesn't line up properly, is the problem.
2. It requires good masking techniques, else anything lit by the light painting that's behind the subject shows through them like they're a ghost, which is just more work in post, especially when it's not necessary.
Major benefits of light painting in a single shot while the subject is in the frame while light painting:
1. The subject is lit appropriately by the light painting, mentally placing the two together for the viewer in the image, as they belong.
2. Free-form light-painting in front of, behind, above and all around the subject is done without any need to mask in PS later.
3. With the subject in place during the light painting, there's no guesswork about where the light should be painted in relation to the subject to get the effect one is looking to create.
Contrary to claims made, moving the subject in or out of the scene while the shutter is open is not at all necessary (see video example above), and is not recommended because of the ghosting effect primarily. If they remain in the scene while light painting, they become their own mask.
Also, there was some talk about how not "clear" the photo was, and the red tint. That was most likely done purposefully in post and had nothing to do with the light painting technique at all. In fact, that "look" is very popular these days, and there are literally hundreds of actions and plugins specifically made and sold to achieve that sort of effect with a single click. I've heard it said that it makes the photos it's used on look like they're old or expired film, light leaks, or just "romantic". It's not my thing, but it's a very popular look these days nonetheless.
While there can be many ways to do something, some are considered better and therefore more widely accepted and used than others, based largely on the knowledge and experience gained by those who've done a lot of work with them and then passed it on to others who then try to improve on it. Reinventing the wheel from scratch can be a very good learning process though, and everyone needs to take the path that works best for them.
I myself learned a lot on my path to creating this self portrait in one frame, though I did take the advice of those with more experience than myself before undertaking it:
I've always found it particularly interesting that the trees, ground and leaves in the frame all take on the light from the light-painted orb I made during the exposure. It puts the orb IN the scene with all of it's surroundings, solidifying the image as a whole. As I was the person making the orb in the dark of night, I was unable to take my place the whole time to be similarly lit by it the way the rest of the surroundings were, which puts me slightly out of place because of it.
At the end of the light painting of the orb, I posed in a spot I predetermined so that I could avoid the ghosting effect by not having any of the orb behind me, and lit myself by remote triggering two speedlights.
It's a lot of fun, a great learning opportunity, and well worth the time and effort to try it all for yourselves, whatever methods you undertake to use.