Advice on colour.

Hello. I'm someone who has been editing for a little bit (mostly short films) but have recently taken the step into promotional work. I want to improve my colour correction and grading to a standard I am happy with but I need a few tips.

First off, a link to a promotional video I did very recently for a local business (didn't charge them so the look isn't a massive issue as they're very happy with it) https://vimeo.com/179942283

Anyways. I'm having a little trouble with skintones. I understand the scopes to a degree, but I'm having trouble altering them without completely ruining the rest of my image. For example, I would put the midtones towards the line but the rest of my image becomes very warm. If I'm shooting for a cooler look in future, what's the best method of altering skintones without majorly impacting everything else?

Thanks guys. Also, any feedback on the video would be most welcome!