[Spuds'n'Buds]

THC degrades to CBD, this can be seen as amber trichs on the plant. So by harvesting as late as possible more THC will degrade to CBD. The only other ways I know of will destroy the quality of your bud, so I won't even talk about them. Also Indica's contain more CBD/CBN then satvia's which you probably already know. So best bet would be to harvest an indica as late as you can for the best CBD/CBN:THC ratio.