Just like in life everything in excess is usually not the best thing. The same goes to artificial lights in photography. I love outdoor portraits, but I also like to mix lights for ultimate control of mood and emotions in my photos. Flash photography is often disliked by many people and the reason for it is simple. It is not about mastering flashes and exposure, but about falling in love with light and effects that you can create with it. Set exposure and measure light with your soul not the light meter. That is the key. Attune to your model's mood or evoke one, whatever you do the light quality should complement it, without drawing too much attention. You are painting with light, not following math equasions.
It depends on the effect you are going for but if you want to create an illusion of natural light with flashes then the key is to tone down the flash power and (often) use color gels that will complement colors or shift them to your liking. This photo that you can see above was shot few minutes before the sun dissapeared behind the horizon. The ligth was too weak to shoot crystal clear portrait but the light color was amazing, and the softness was too good to ruin it. I shot this at 1/250 so max shutter speed that my camera syncs with the flash (HSS would not give me enough power from one flash gun). I had to dial down the flash manually untill it felt right, I do have light meter but honestly I rarely use it. I used double diffusion with CTO gel for the flash to warm the light up. I callibrated WB with XRITE color checker before applying the gel, so then the orange cast would add on top of the corrected color. That gave the illusion of sunset color. Photo was cross processed so the final tones have shifted anyways (see the video below which shows my photoshop editing workflow) but it is important to have a good color base, esepcially for portraits.
Experiment with light and forget about TTL if you are not in a hurry. And quite frankly I never am. I create image after image and time doesnt bother me. I do not care how long I have to shoot to get what I want. Also, you should master photo editing and preferably in Photoshop or any program that gives you superb control over layers and offers non destructive editing. Leave Lightroom for lazy people and those who edit their photos in bulk. They lack respect for their own work. Portrait editing is an art and requires time (see my 5h long in-depth photoshop tutorial on portrait editing), patience and vision. Get it right in camera for me means two things: to capture beautiful light and natural body language. The rest I not only can, but WANT to play with in photoshop. I love doing it.
Go outside and learn how the light works, study it and appreciate what it can do and what you can do with it. You will see world in a completely new light.
Complete portfolio in full resolution: http://ponte-ryuurui-photography.smugmug.com/Portfolio
Photography workshops in Tokyo: http://www.ryuurui.com/photography-workshops.html
Hire a photographer in Tokyo: http://www.ryuurui.com/hire-a-photographer-in-tokyo.html
Photo blog: http://www.japan-in-photography.com/
For more tutorials and how to videos check out my photoshop and photography tips and tricks YouTube channel: https://www.youtube.com/channel/UCEOVGZ2rpLhR7gSPvaexxxQ