I was interested in Hellenic magick for some time, but I never worked with Hypnos. It’s hard to imagine that any Greek deity looks like that. They value beauty so much.
It reminds me on Lord Ganesh. He’s very relaxed about his appearance and has a great sense of humour
When working with the Greek Parthenon deities, it’s good to know they have some sort of family order.
I don’t want to make your life complicated, but consider asking his mother Nyx first, to let you contact him.
People who are deeply in Hellenic Magick recommend approaching to them as they like, usually with a great respect, good manners, in a proper order and specific time.
It always means that ritual should be performed when you are well prepared.
The ritual should be memorized, cleansing is a must, as well as a clean robe (they find wool and leather to be impure).
Ritual also should be done barefooted. Sexual abstinence and fasting are also recommended.
Offering in an appropriate form is very welcomed.
Keep in mind that Hypnos is related to sleep, while his twin brother, Thanatos to death. His whole family is related to the underworld. Many other Greek deities, including the supreme one, feared to enter their realm.
From my experience, it’s good to get informed as much as you can, because Greek deities have
complex relationships and it should be taken seriously.