It depends on what the source of the pain is. It could be a bone spur, or a bruised heel, or a wart under the callus. Or something else. In my case, I got it bad a few years ago, starting on a rapid descent of the trail from El Capitan. Over the following months, it just got worse and worse during any long hike. It turned out to be plantar faciitis, which is an arch ailment (though the pain is in the heel). There is a ribbon-like tendon that ties the forefront of the foot to the heel and keeps the arch from going flat. If that's what you have, you can pad heel all you want, and it will not help at all. I fixed mine, over a few months, by wearing high arch insoles with addition arch pads on top. Basically, I can feel them press on my arch whenever I walk. That takes the pressure off the tendon, since the arch is no longer trying flatten out when you put weight on it, so that tendon is no longer trying to fight that force. All my shoes now have extra arch supports, and I never stomp around the house barefoot.
The good news is that the problem has completely gone away. The heel does heal.
Your problem could be something else. But if it's plantar faciitis, you'll never solve the problem by cushioning your heel. You have to fix the arch.