Hey I was planning on leveling up a milotic tomorrow and was thinking this build

surf
icebeam
hypnosis
rest? When you use rest do you get the defense bonus from marvel coat?

Yes, you do get the defense boost. I would recommend using that with Sleep Talk so that your Milotic doesn't become a set-up bait when it is Asleep.

So, I think the moveset should be like this:

Surf
Ice Beam
Rest
Sleep Talk

Remove Hypnosis, because its accuracy is a low 60 %, and as such, it is unreliable.

Would that setup make use of marvel scale?

Yes, as when Milotic is asleep, it would get a defense boost. That way, it will be difficult to take down, without being a set-up bait.