I have spent a lot of time and effort on this very subject. You’ll notice that the clear resin models are in fact clear during the build and when you rinse them in isopropyl alcohol. When they are wet, they appear clear. When they dry out though, the surface looks just like your models.
I was intrigued by the article on hackaday.com that refers to a surface smoothing method using vaporized solvent. See http://hackaday.com/2013/02/26/giving-3d-printed-parts-a-shiny-smooth-finish/. To test out the process, Since I don’t own an ABS printer, I used a lage candy jar on a hotplate to smooth scratched Plexiglas with methylene chloride. It worked like a charm! Unlike the ABS plastic models they refer to in the hackaday article that are soluble in acetone, our photo polymerized acrylic FormLabs models are resistant to pretty much any solvent. (I went to a forensic laboratory myself and tested the solubility of supports in test tubes with about 20 solvents, some quite exotic and most very dangerous to work with. No appreciable solubility occurred with any chemical.)
I tried polishing the models with a variety of pastes and fine abrasives. Polishing kind of works, but it’s nearly impossible to work in small recesses and friction heat is a huge problem.
What turned out to work the best is Kylon acrylic spray. I put my models on a record turntable and just spray the models with an even coat of acrylic spray as they slowly spin. Sometimes two coats are necessary. It fills in all the minute gaps on the surface and amazingly, the model is clear again like when it was wet. Too simple…