The way to promote OC is to do it.
An important aspect of "promoting OC" is to not have laws that criminalize it.
Obviously, it is quite difficult to OC in Florida with their effective ban on OCing. Ditto for OCing a handgun in Texas. Some minimum level of OC-friendly laws are needful. Some effort to get them, retain them, and then expand on them is required.
If OC is legal without a permit, keep it that way.
Make sure that getting a permit does not impose an extra burden to conceal.
Work to avoid having criminal penalties for private gun bans. Go a step further and work to have private gun bans outlawed just as private policies enforcing racial discrimination are illegal. Get what you can get.
In Utah, with the exception of private homes and churches that give notice, private gun bans carry no force of law. That combined with culture means that very few businesses bother to post, and if they do, there is still no violation unless the specifically trespass you and you refuse to leave or continue to return in violation of the trespass. Even then, no gun violation; a trespass violation only.
We do not (yet) treat gun carriers as a protected class in most cases, but we do have parking lot preemption so that employees can store a gun in their cars in company parking lots without facing employment action. This makes it easier to have a gun for lunch-time efforts, after work rallies, and for general self-defense during the commute.
Work to reduce the number of off limits locations. There is no reason for parks, hospitals, most government buildings, libraries, or schools to be off limits. At the very least, get off limits locations exempted for permit holders. Now you can legally OC in places you couldn't, so long as you have a permit. Yes, this is constitutionally offensive, but often more politically achievable than "allowing just anyone to carry a gun into a school".
Bottom line, the fewer legal restrictions you have on OC the easier it is to OC, the more people will do. If the only way to OC is to devote a lot of time planning your route and what you'll do with your gun when you get to destination X, fewer people will carry less often.
I'd dare say that in Utah, the vast majority of our regular OCers have permits to carry so as to be safe with school zones (
LOTS of schools here), to be able to carry fully loaded rather than "Israeli" or Utah-unloaded as is sadly still required even to OC without a permit, and for reciprocity reasons. With a permit in Utah, almost no place you commonly go where you can't legally OC.
Just some thoughts.
Charles