Kal, what I've done before (with success) is to basically assemble the shroud (without the fan blades), then split the shroud with a razor saw (inboard to outboard) about where the fan meets the innards of the cowling, finish the interior surfaces, and then assemble later.
So......putty, sand, prime and paint the inside of the forward cowl. This means you have to glue,attach, fill and sand the fore part of the cowl to the rear later.....but it gives you a chance to make the insides all pretty and perfect without having to mess up your fan blades.
It seems like a real nasty chore (when you hear it), but have a look at the structure....it'll be easier than you think....and you'll get a great result.