You display your models in open cabinets where they collect dust and more dust?   For me, if it don't fit inside my dust free cabinet, then I don't build it.  I figure, all the money,time and effort building these little models just to let it collect all that dust and possibly mess the paint job?  
  
 I just put some weathering foam strip around the regular cabinet glass doors (not an expensive cabinet) and it keeps the dust out and the little models look always like new.  I used to just clean them with a soft brush but got tired of it.