So one of the joys of having a dog is being able to travel with it. It can be a real drag if your dog is afraid of the car or refuses to get in its little carrier bag if your dog is small enough to go in a carrier bag. Especially a little guy like Dexter, he'll be small enough to fly in the cabin of an airplane, but if the first time he's ever in a travel bag is to be on the cabin of an airplane, he'll probably be really stressed out by it and make an awful lot of noise and commotion. It will be an unpleasant experience for him and you both.
So getting the dog acclimated to some of these things before it's a long road trip. Some dogs get carsick in the car, and it makes them uncomfortable. So you may need to do short trips with your dog. Maybe just take them to the post office and back or something, before you're going on a four-hour trip someplace, or he's going to throwing up all over your backseat. Making sure that the dog is accustomed to the travel bag, the car, or just even if your dog is able to come with you into the bank or things like this, things that you need to prepare your dog for in the long run.
So make sure the dog is safe. Make sure that the space it's inhabiting in the car is cool. You're not in a parking lot with the windows closed on a sunny day. Or if the dog is in a bag, he doesn't have anything that they can chew on that could potentially be dangerous, whether it's a squeaky toy where the squeaker can be removed or something plastic that might not be appropriate for chewing when he's unsupervised. Stuffed hollow toys are a great way to keep a dog busy in the traveling bag or in the traveling crate and keep the experience a positive one.
If you are flying with a dog that's too big to fly in the cabin, just do as much research as you can. Speak with the airline at length to make sure that the dog will be safe if he's flying below the airplane. You don't want the experience to be unpleasant for your dog, where if you're going to travel with him anywhere you have to drug him up or something. You want it to be something that's pleasant for you and your dog both. So that's how I would start, and that's how you would travel with your dog.