One thing that I was extremely remiss to talk about so far is car work (Ali Brown writes extensively about this).  I like to use car work as foundational steps to generalizing behaviors and teaching pups that regardless of where we are, it pays to focus on me.  I use this in everyday life not just for reactive dogs but it can be a great tool to prevent the hypervigilance, over arousal, and potential barrier frustration that can occur with the different types of reactivity.
For me, one of the most important skills a dog can learn is a default focus behavior–the dog doesn’t know what to do so they default to giving the handler eye contact.  I’ve found that dogs have a hard time escalating to a reaction when giving consistent eye contact to the handler (ie looking away from the trigger).  Some of the car work is also really great impulse control practice as well–which can be very beneficial for arousal and barrier frustration based reactivity.
Now, the following is a very limited look at car work–if you are interested in a wider scope of using vehicles in working with fear/reactivity/aggression, I’d highly suggest reading Ali Brown’s Scardey Dog and/or Focus, Not Fear).
Perhaps the most foundational use of a vehicle is creating that default attention.  My verson works like this (I think it is slightly different than Ali’s but I cannot recall the details)… you drive to your destination, get out of the car and then let your dog out of the car.  As he/she exits you call their name… you wait (no second cue no prompting)… if after 10 seconds your dog doesn’t orient to you… cue the dog back into the car and shut the door for 30 seconds.  Then let the dog come out, call their name, and give 10 seconds to respond.  If the dog doesn’t respond with eye contact, they get cued back into the car for another 30 seconds.  If the dog responds, click and treat, if the dog goes back to looking away, call their name and give them 10 seconds to respond.  If no response, back into the car, if they respond click and treat.  I click and treat for continual focus for a minute or so, then I ask for two simple behaviors (say “sit” and “touch”), then I take a few steps forward stop and call the dog’s name.  I give the dog 10 seconds to give eye contact (not just a flash of eye contact), if there is no eye contact the dog goes back into the car.
Now the important thing to remember is to keep your criteria clear.  One name call (*make sure the dog has good name recognition first), no kissy-noises, a set time (I use 10 seconds), and consistently having consequences for not giving eye contact.  When you call your dog back into the car, you shouldn’t be yelling or dragging them in, just simply cuing them.. back in and latching the door (no slamming).  When I put them back in the car, I latch the door and wait 30 seconds, if the dog is really overwhelmed/aroused, I may let them settle for up to 2 minutes, but that’s not too common.
Eventually I stop cuing them with their name and just wait for eye contact.  When they understand the expectation of reorienting back to me, I simply stop using their name to get their attention.  I let them out of the car and wait for 10 seconds, if they look to me click/treat, if they don’t, it’s back to the car for 30 seconds.  When I have their focus for the initial minute or two after exiting the car, and the dog can easily focus to do two simple behaviors, I start moving away from the car.  I don’t require a heel but no tension on the leash.  After a few steps I stop and give the dog 10 seconds to give me eye contact.  If they look back click/treat and continue forward, if they do NOT look back within 10 seconds, it’s “too bad” and back to the car they go. If there is any reaction or increase in arousal, I bring the dogs back to the car to calm down and start over.  All of this should be done in a controlled environment without the major trigger at first–step one is building the behavior and setting the expectations.  When they are reliable in a lower value place or without triggers then you can either go to a more exciting place (maybe a favorite hiking spot) or introduce a working with a trigger at a distance.
The end goal is to have a dog who isn’t becoming overly aroused or hypervigilant at the very beginning of any experience (just getting out of the car).  About having a dog who, instead, chooses to look at you and pay attention to you in the face of great distraction and is learning some impulse control by giving an alternative heavily rewarded behavior.  So even if there is a trigger in the distance (at a distance that is still sub threshold for the working dog), the dog can get out of the car and make a choice to orient to you and not react because we’ve given him/her an alternate rewardable behavior.