I hoped to be clear here and on Shapeways about materials and models in prototype stage:
WSF polished is more "smooth" than WSF (smooth as a 400 sanding paper is) but not as smooth as plastic (only very high quality prints like those used to create casting masters can achieve that and price is prohibitive).
To have a smooth feel in WSF polished, you need to coat the model with resin (or a thick paint or varnish layer, maybe multiple layers if needed to fill the irregularities) then sand it. Liquid GS or Vallejo liquid mastic may works too but I didn't test them (I will post a tutorial if I have time for it).
FUD and FXD are the closest way to achieve the smooth feel (even if they are not totally smooth), but the price is higher (at the moment). Once the shapes will fit the cockpit at 100% (latest prototype is inbound), I will release the weakened but hollowed model (which will be around $9 in FUD, cheaper if taken bundled).
For the prototype, I used a nearby printing services via 3DHubs
in a Form1+ SLA grey resin printer in 0.025 mm / 25 µm (some services propose cheaper prices than Shapeways, other not and quality/service may vary). You need the STL file to upload there (PM me to have access to my latest prototype so far). Details are good and surface quality is equivalent or better than FUD (not totally plastic-smooth but looking quite fine). The service I used have reasonable prices but is located in France....