You might be able to get good results by posing it, then exporting the mesh, with all vertices welded, no other options, as a wavefront .obj. Then, import that object. If Poser doesn't automatically assign it the same material settings, you'll have to reassign them. Then, go into the Cloth Room and Clothify it and muck around with the simulation settings to see if you can get some slight, squishy, draping effects.

You may also be able to use this, though it's only in beta atm and I don't know what features are inhibited atm - https://www.renderosity.com/mod/forumpro/?thread_id=2891120 (You'd be able to bypass the export/weld/import step completely with this, I assume.)