VERY hard, Lavender. I truly don't know the answer. My success a couple of times, quickly getting over intense pain, was for conditions that typically don't last more than half a day or so in any case (menstrual cramps, way back in the day; an intense headache a few years ago).
But mind-over-body techniques should be able to help somewhat. For example, someone might try countering the panic messages from the brain, by talking back, telling it "This amount of pain is not necessary! I'm safe, I'm doing what I need to do, shingles are not life-threatening, and it will pass".
"This isn't necessary" is my favorite talk-back phrase, and it's pretty effective whenever a symptom pops up.
Visualizations are also very powerful. For example, staying hydrated is almost invariably a good thing, so as someone is drinking plenty of water, they might visualize it flushing out and soothing all the systems of the body and helping the immune system beat back the attack of the virus.
These seem like little things, or kind of light-weight, but they absolutely can't hurt, they are totally free and non-invasive, and they could possibly help.