Opinions on what the hull of a starship would feel like, if you touched it 'First Contact' style with bare hands? Like ceramic (rough porcelin?), plastic (like Rubbermaid container or an iPod), or like the painted finish of a car? Personally, I like the ceramic option -- some sort of thermal coating. I don't know if any Trek authors ever tackled this.
One thing you have to consider is a phaser or a cutting beam on on a ceramic surface or the burn marks from explosions and phasers blasts. I might go with the idea that the metal surface is one color for a certain depth (maybe all the way through). It may be advantageous to be as smooth as possible.
It's been mentioned onscreen that the hull is made of trititanium (fictional alloy). Which I'd like to think is some sort of ceramic titanium alloy. probably looks like metal but feels like very thick glass.
I think the later Trek shows have implied that starships hulls are made of different materials, including varying amounts of tritanium, duranium, and other metals and composites. I would imagine the hull of a starship would feel hard myself. Personally, I would imagine a starship hull would feel like the Saint Louis Arch (most visitors there always touch one of its massive stainless steel legs). It's smooth, but your hand doesn't necessarily just slide off of it, IMO.
Duh, I completely forgot. These ships are painted. They'd feel like some sort of 24th century starship paint (protective coating). With the aztec hull patterns we've seen since TMP, maybe the hulls are actually tiled like the Space Shuttle. Nuclear submarines are tiled too, just with different material. I've been to the Arch and touched it. Good comparison. Hell of a tram ride up though.
Picture the face of an old fisherman, weather beaten and proud of it. Always kind of imagined that up close it was rough, like old freeway asphalt. Pitted, beaten-up, scarred. Even with the screens and shield it had taken a lot of abuse, the energy that gets through during battle has caused the hull to thermally expand and contract resulting in the outer most layer to hold cracks and small grooves. Times when the defenses were down to use the transporter mirco-meteorites and the solar wind would also take their toll. But the hull is thick.
^well, that's the point of tritanium and other metamaterials, to handle stuff like that. Materials science has been what has allowed humanity to build the modern era. Fabricating iron objects and later jet engines were quantum leaps made by new materials. I would imagine a starship Hull would be vastly more alien than modern composites, though I would suspect the Hull material would also be composite. A hard outer layer to deflect small fragments on top of a metallic material that holds the Hull components together when stationary. Then you have built in structural integrity field emitters too, and an anti-radiation material, and it would be self repairing to an extent. It would likely be surprisingly thin and light for what it does. So is it ceramic or metallic? Both probably. Could even be a metal with an atomic structure similar to a ceramic (there's a company called Liquid Metal that's been doing stuff like that for years). It will also have integrated electronics and things we can only barely comprehend.
As good as materialscience is, even your car finish has imperfections from... mini-mini bits of iron, grains of dirt that get rubbed in... aircraft finishes aren't silky smooth, there's imperfections. So I imagine the materials science that creates superhard super strong things will again face tremendous strains that prevent the showroom shine to last past Spacedock. One reason why I like the finish change for TWOK.