I don't think you need to boil it after every application. Just once at the end. I did a barrel and lock using LMF. I did four or five coats of LMF, and only boiled once at the very end.
Also, to do the barrel, I bought a section of PVC pipe about 2.5 inches in diameter and a few inches longer than the barrel. I glued an end cap on the bottom. I put my barrel in it, then filled the tube with distilled water that had just boiled. I left it there for 20 minutes. Worked great and gave a nice deep black finish.
Cheers,
Norm