The last time I painted the black stripe between the hull "red/grey", called boot topping, was in 1963! I was still in deck division, and hand applied the boot topping from a "camel".
Ed has the right idea. Somewhere here there is a discussion about drawing waterlines, that will help place the masking, the boot topping runs from the waterline, up about 8" as I remember. The real stuff is glossy, so I would think a semigloss for the model.