I would mix into the meat prior to cooking
I'm a son of The South, and barbecue is a staple of life around here.
Most meats are cooked outside on either a gas grill or on a Weber grill with charcoal. It's nice to have screened porches to protect us even in times of bad weather.
We simply don't use Liquid Smoke. That includes barbecue sauces with liquid smoke in them. I just can't stand the taste.
Umm, guys I worked in the largest spice and flavor company many years ago and know a bit about that "stuff". Try this on, employees creating and bottling it were required to wear full body protection and masks if they worked anywhere near it. Eat it? NO WAY!!!