I can't offer an autism perspective, but I will say that figuring out what you like and don't like is a very common issue and unique to each couple.
My own wife does not have autism, but also is extremely sensitive and cannot handle anything but very delicate sensation. Over time we've just figured out through experimenting what works for her.
I don't think anyone could have taught us - it was something we had to figure out together.
So, my long reply short: you are right. Try things out and see what works. As long as you are listening to each other you are on the right track.
Well, nothing very groundbreaking, honestly.
Her preference is most any kind of contact with labia (she finds they're not as sensitive), which would mostly include licking (mostly midline, from introitus towards clitoris) or lip to lip, like you're kissing the labia like a mouth.
For direct clitoral simulation she prefers very gentle kissing of it, and eventually gentle licking (either flicking or circular around it) or sucking.
But again, the pace, intensity, pattern is very individual.
I might suggest just looking up oral sex guides and then seeing if any parts of them work for you.
Ah I see.
I wouldn't have any recommendations for addressing smell - one shouldn't try to change the smell or taste of a vagina, in particular.
For taste alone, if you've bathed before, the clitoris and penis shouldn't taste much different than any other skin - but maybe you find mouth kissing difficult too? I'm not sure from your original post.
Texture again, shouldn't be too different from other parts of the body, but if you find all of it overwhelming it may just not be very accessible.
Similar to learning what your partner finds enjoyable, over time you might find the pleasurable aspects override the overstimulation. But, my training isn't specific to autism, so you could certainly correct me if you don't find that's true for yourself.
I'm assuming mixed gender but if not just take the relevant bits.
If it's a smell and taste thing I have a few tips.
First hygiene. For a guy make sure you wash with soap and water and if uncircumcised pull the foreskin back and rinse. For a lady get a good rinse. Spread the outer labia enough to get a decent rinse.
Next even if you are in relationship where you are comfortable with unprotected sex unlubricated condoms and dental dams can help reduce taste and smell. You can even add flavors you like to the side in contact with the mouth.
Third don't push your self to hard to handle sensory stuff you dislike. Better to stop early before you have a big negative reaction then push through and develop extreme negative feelings.