Great question.
Starting with the easier one, I don't know how to accomplish it with transcraniel magnetic stimulation, other than that, it can produce altered states of consciousness similar to psychedelics. I don't think we have enough insight into knowing how to adjust settings for a particular person to reliably get certain shifts in consciousness. Perhaps investigating along the lines of why and how someone can experience synthesia.
As far as psychedelics goes, we'd probably have to delve into the traditional practices that works with altered states of consciousness, and that all depends one one's tolerance for experiences that would be considered woo. Two that come to my mind are Tantra, and the shamanic practices involved with "shapeshifting" into animals.
In Tantric philosophy, pure consciousness descends into the manifest world through the five senses, and you see those representations as five downward triangles in the yantras. There's probably some yogi out there that have explored along those lines. Tantric methods can involve offerings of flowers and incense, so why wouldn't smell be involved?
With the shamanic practices, with the assistance of drumming or psychedelics (and keeping in mind the basis for shamanic practices is animism), the practitioner would seek out the archetypal intelligence of an animal, and request to form a relationship. If granted, one of the ways the practitioner learns the wisdom of that animal archetype is a kind of shifting of consciousness into that of the animal, while partially retaining the perspective of a human. If that animal's olfactory senses is a big part of its role in the ecology it inhabits, and the human is receptive to that, I think it is possible to experience what it is like to have smells that is usually inaccessible as humans.
As far as human's ability to process things with visual and auditory senses ... I'd say that whales and dolphins probably got us beat as far as auditory intelligence goes, and birds has us beat as far as visuals goes. Bird brains also seem more efficient than humans in terms of energy usages, and birds have to process five retinal cones compared to our three retinal cones. The unusual humans who have fully formed fourth retinal cones can already disginguish significantly more color tones than the rest of us ordinary humans. If someone wanted to experience what superior visual and audio experiences are, I'd say try the shamanic techniques to shapeshift into a whale or a parrot.