Hi Crow, with regards to trying a vibrator, we have an article on Scarleteen that has instructions on how to safely make and use a DIY vibrator here, which you may find useful for your experimentation: D.I.Y Sex Toys: Self-Love Edition
As you mention, being neurodiverse is something that can effect our sensory processing in a variety of ways. It is great that you already understand that in other contexts that this is often, for you, linked to hypersensitivity or over-stimulation, and earlier you mentioned that you are still working out when you will feel recharged vs. drained by certain activities. That's some really awesome self-awareness and understanding of yourself!
Our brain and mental state is an important part of our sexual response cycle (if you're interested, this is explained in depth here
, and here
). Sometimes it can be stress/putting pressure on ourselves about feeling pleasure that makes it hard for our brains to respond to masturbation (as their too busy being stressed). Also, we all have different relationships to activities depending on context, and how we're feeling (like your drawing vs sculpting example), and it can take some time to observe those patterns and they can be tricky to discern, for both neurotypical and neurodiverse folks. So it is totally okay for this to take time, although it is certainly frustrating whilst you are in the middle of it all.
Given that you already understand your individual sensory processing with regards to other physical sensations, do you have a therapist at the moment, or have seen someone in the past, who has helped you better understand your sensory processing and neurodiversity? Masturbation and sexual response is definitely something it would be appropriate to ask someone like this about, as they can approach it from this perspective as well as with regards to mental health/working through your thoughts and feelings about it also, with you. What do you think of this idea?