By ladders are you referring to the layering that is visible due to 3D printing or the ladder style supports?
I use an automotive type primer with filler that seems to hide some of the layering when you prent at higher resolution, but it can also dull details in the print. This hasn't been an issue for me in terrain, but could be on 28mm miniatures. Someting I have seen recommended is to first coat the mini with polyurethane to fill the gaps on layering. I suspect this will work, but would likely dull details even more. I have some that I am meaning to try on simple terrain pieces printed at low resolution for speed.
If you are printing with ABS you can wash or fog the print with acetone to melt the ridges down. I haven't tried ABS yet, so haven't done this myself. I am not aware of any solvents that are readilly available that can be used to melt PLA in the same way.
Another thing I have yet to try is the ironing feature in CURA which basically uses the printers nozzle at the end of the print to go over the surface an re-melt the plastic to smooth it out. My understanding is that this works best with flat surfaces horizontal to the print bed though.
For my UV resin printer, it seems that brushing the model with alcohol (at least before it is fully cured) helps to smooth out the surface.
As for supports, the software for my resin printer let's me build supports that are easy to remove. I have yet to find an acceptable support in CURA for the filament printer that is easy to remove as I am trying to print some cheap minis on it...so far it is not going well.
Above all, the desigh of the print goes a long way toward getting a nice finished product. Companies like Fat Dragon and Printable Scenery seem to do a good job that make the layering less obvious in the finished product.
regards-Mike
