the way I understand it is:
1) DECARBOXYLATION: removing carbon dioxide from THC-A to convert it to (biologically active) THC,...this is done with heat, either buy burning, like in a pipe, joint, bong etc,..., or by heating in an oven, or in a lipid such as butter or oil (I hear coconut oil rocks), with the oven/butter methods intended for ingestion.
2) ISOMERIZATION: in the plant CBN degrades into THC-A, which dries, and loses carbon dioxide, then becomes THC (as above) and then further degrades into CBD (if I got it backwards someone will correct me, I'm rather medicated) if your plant has a LOT of CBN, you can "FAKE" the degradation by adding a strong acid (I used hydrochloric when I did it) in a reflux setup with a solvent, this adds a double bond on the benzene ring or something like that, and makes a molecule that is an isomer of THC (great explanation, huh?), so you end up with almost no CBN, because it's now converted into THC-isomer, which WILL get you baked, because your body cant tell the difference between it and THC,.........the trouble with this is most weed in the last 30 years has very little CBN even when picked early, so isomerization will work AWESOME if you have a field of kentucky ditch weed (wild hemp, considered a nuisance, grows all over the state), but not so great on your "crap I got mites, I have to harvest 25 days early" northern lights super dank,.......but it will increase the potency of the extracted oil, by the factor of how much CBN was available when you did the reflux/isomerization.
for the record, I never put the extracted "honey oil" back on the buds, I just mixed it with some dry sift to make what we called "putty", but is now referred to as jelly hash.
I hope that answered your question,.......you can read "marijuana chemistry" by michael starks, he has a whole section on isomerization, pretty well written, and is where I learned about the process WAY back in the late seventies