Sandpaper on proper supportive blocks are your friend for blending shapes. Use fresh paper and a light touch rather than forcing old paper and it'll help a lot.
If it's solid wood then something like 1/2 oz glass cloth doped onto the wood will produce a nice easy to form skin. Follow that up with some talcum powder (Baby Powder) and dope as a coarse sanding sealer. When dry overnight sand with 400 grit paper but try not to cut into the cloth by much if any. Just until you can see the tops of the weave barely and then stop. Allow to dry for about 2 weeks and then spray with 2 coats of automotive primer. Allow to dry for a few days and then wet sand with 600 grit paper. No weave of the cloth should be visible or you need to spot touch the primer and lightly re-wetsand. When smooth as the proverbial baby's bottom (where you stole the powder from
) then it's time for spraying on color.
There's probably other ways and other materials but the key is to cover the wood grain with either fabric or paper. But in my experience the super light 1/2 oz glass cloth will form to most any shape and so it's what I think is best for complex shapes.
To tell the truth if I was making static display models I'd use basswood. The super fine grain would not require any fabric or paper covering. Instead just a very light coat of epoxy laminating resin that is then "blow dried" with a hair dryer on high heat to warm and thin the epoxy so it penetrates the wood better followed by the sanding sealer and paint would do the trick nicely.