That's what I would use is a brazing tip on a torch where you can concentrate the heat on the nut. If you could drill a hole in the end or grind the end off so you could get some penetrating oil to the threads would really help.
I mentioned using Nevr-Seez on my lugs on FBBO and was immediately told I'm an idiot and you couldn't do that as the nuts would come loose. Obviously this person never lived in rust country either, because if you didn't use Nevr-Seez on the semi lugs you would never get them off after one winter except with a torch. I've been doing that for 50 years and never had a nut come loose.