MDO (sign grade - smooth) plywood would be the way to go, but it's like 4x's the cost of OSB.
CDX plywood isn't that much more than OSB and might even save you money on paint.
I researched this topic not long ago and found a few examples of black paint on OSB, followed with a semi-dry roller of white paint to bring out the raised highlights. Gave it a sort of Tectum look to it.
Cabmando, that's an awesome look.
EDIT:
I was thinking that a heavy stain blocker primer could seal up the OSB early on so that it would not soak up so much paint on the finish coats. I found this article that has some suggestions, but have to admit that I've never painted OSB myself. I do like the wonders of using stain blocker as a primer in some situations though.
How to Paint Oriented Strand Board
https://www.doityourself.com/stry/how-to-paint-osb