Heya,
With that setup, you might want to add a light meter, it will speed up the process and make it accurate for the first shot, instead of chimping all day. Biggest life saver in lighting in my opinion after having done it without one for so long, then got one and immediately wondered why I waited so long to get it.
So, there are not blanket settings to apply. It all depends on the ambient light and your sync speeds.
So a few things:
1) In the shade, with a synch speed of 1/180s on the 6D, you may find that something at F1.4 and F1.2 is too bright even at ISO 100 when you meter the environment. You may have to stop down to F2.8 or use a ND filter to drop ambient light more while staying at your top sync speed. I doubt you'll need a slower shutter at F1.4 and F1.2 in shade outdoors on a sunny day. On a very overcast day in the shade, you may have less light and get away with those apertures at a slower shutter speed.
2) Natural light is a natural rim/hair light, so pay attention to it's placement in your composition. This will also help you do the key or fill light with your flash. It will have to be close proximity to your subject to actually do more than just fill on a sunny day even in the shade (ie, not 12 feet away). 4~5 feet away should be able to work out depending on how bright it is outside. Closer is better though, softer light, and the modifier is larger for the distance the closer it is to the subject.
3) Fill light is generally about -2/3rds to -1 stop below key exposure with your flash, just enough to fill shadows, but not enough to be a key light. With a light meter you can nail this in one go. Without it, you have to just chimp and look at your histogram & LCD to judge it that way, which is inaccurate, but it's all you have.
4) Gels are important when blending flash & ambient light. Flash temp is generally daylight temp. So if you're shooting in shade or middle of the day light, it should be fine. Late evening light when it warms up, that's where it will be an issue to shoot with cold flash temp light. So a 1/4th CTO gel is nice to have if you're shooting late evening light so you can blend it in and not look like obvious "flash".
5) Practice, practice, practice.
6) Practice.
7) Light meters help a ton to speed this process and make it accurate without chimping all day and losing light. Cheap investment compared to what you're shooting with!
Very best,
:: My 
