I smoothed off the filler and carbon fiber, then removed the vent from the mould. Alas, I soon realised that it would be better to lay up on the other side of the mould, so that the smooth surface is facing out ... on the side where it will be painted.
I then decided that result would also be flawed, so I decided to make individual moulds out of the louver fingers. This will take longer, but the finished product will be much better and I can adjust the rake of the louvers to my liking before they are trimmed and bonded to the cowl.