With all due respect to Rick Simpson, isopropyl and naptha are not food grade. Naptha in particular is a fraction of many different petroleum products. Not all of them will boil off. Boiling off the solvent will not decarb, but he does a long "purge" that is equivalent to it.
This process makes a tincture, and there is still solvent present. Do not ingest ISO or Naptha! If you want to make Rick Simpson's oil, I would use Everclear.