I use a lot of stretches, my hot-tub, and the side of my pickup bed. The hot-tub has an extended vertical feature that is about 4 inches wide that I can stretch my back over while sliding down it, and it pops almost my entire spine back into place. I use the pickup similarly when traveling.
To treat a hiatal hernia stand with your back against a wall, bend over slightly, and relax your stomach muscles. Then with both your thumbs press in on your solar plexus like you are trying to touch your spine with your thumbs. Then slowly slide your thumbs down towards your navel. As you approach the navel push down to the left. Repeat two or three times.
You should feel immediate relief. Eventually you will be able to tell when you need to do it.