I am so envious of this! 🙂 I have never had a Buffyverse dream and I feel like it would be very helpful for my writing.
I am definitely going to try this!
While I haven't trained myself for recreational dreaming, I have for therapeutic purposes. Long story short, I took to using self-hypnosis to "program" a dream in, "play" it, and "program" it some more. Then I'd write the events as if recalling the dream. I think some earlier training in meditation (of trying to stop all thought, primarily focusing on breathing, a mantra, and a timer so one doesn't keep looking at the time) was helpful to this, but I don't know. I was trying to stop my horrible, horrible nightmares, and it worked slowly and surely over the years, and interesting enough it helped me a lot with my waking PTSD (*). The point being, if I could use that to heal up intense psychological trauma, then surely you could adapt such a process to get yourself to dream more about Buffy.
(* For anyone interested in that, the very short summary is that part of my brain was "stuck" in certain incidents of the past in which my personal reality at the time was in force rather than my current, so I could be a helpless kid who could not lock doors behind me, so I'd work on making doors work during self-hypnosis and "rewriting" the nightmare. Any instinctive attempt to fight was doomed in such nightmares, and guns I dreamed of using were useless because those were not part of my reality back when the traumatic events that caused them happened. As the repetitive nightmares changed, I got where I could fight back and that was much less horrible, though still bad.
Interesting enough, I also fought the nightmares of fire in my dream and in my dreams I'm not pyrokinetic, though I can "only do it a few times, so best pace myself" before I have to "recharge" and often linked to brief abilities to fly, so if I "fly to a roof" then that drains my dream-self as if I used a pyrokinetic attack on a monster.
After years of slow improvement, I was in the home stretch and worked to finish them off completely as an empowered adult no longer in peril and haven't had the horrific nightmares I used to have frequently in years, though sometimes I get a pale imitation of one...especially in October when they're at their worse, though I don't recall any this month yet! I always get superstitious about talking about them in October, though...and it seems the bulk of my PTSD has also been overcome, because I "untangled" the memory of the trauma in my mind, and my brain doesn't have to perceive it as I did as a kid.)
Also, Vitamin B12 has worked for more than one person remembering their dreams (the melting tablets work best), though many people then discover just how boring and tedious most of their dreams are!