This is for Dee. I couldn't respond to your original message, because there was no Reply button. Did you get any further? You're on the right track. Light the torch at the bonfire. It only stays lit for about 10 turns. Take it to the skeleking in the past, then revisit him in the future.
It's a similar principle with the exslowsive. Drop it somewhere that needs to be blown up in the past, then revisit it in the future.