Are you going for traditional flying ointment, or something to give amazing dream state/trance experiences?
The reason I ask is because all true flying ointments are going to have something highly toxic in it, like the belladonna you mentioned, or henbane, hemlock, foxglove etc. So if someone is billing something as flying ointment I would be skeptical if it is non-toxic. True flying ointments are hallucinogenic when used, in or out of ritual. There are some good recipes out there but I would be VERY scientific about it. The recipes with unwashed poppy seeds are interesting.
The real stuff? Never put it on the skin near any glands or mucus membranes, or on the groin or armpit. You can really harm or even kill your self. When I experimented with salves I would rub them onto the underside of my wrist and forearm. First a small bit on the arm, then a bit more on the wrist once effects are assessed. ONE ARM AT A TIME.
For lucid dream state/trance experiences a 50/50 mix of mugwort (artemisia vulgaris) and dream herb (calea zacatechichi) smoked and drank in tea before sleep or trance can be truly inspiring, and it is absolutely non-toxic. The tea is super bitter, though.It is basically a hypnogogic hallucinogen. When I have used it it makes me a bit cheery but very laid back, and when in trance I have gotten anything from a kind waking dream to flashes of images with strong or weaker symbolism and relevance.
Consequentially, that combo is a great herbal loose incense base recipe for lunar or astral workings.