I think I now understand what you meant by 'solid': the open spaces where you created the room to get the walls, that you would like to be filled in. The room you used is not a regular room, it is the 'inside' of a very thick wall.

Here's a trick to create your solid walls: You already have the walls, select the create room icon and click on a wall, not inside the walls. It will create a room with the outer circumference of the walls. Export/import, change the height to the height of the walls and you have a solid wall.
Remember that this is now a normal furniture object without the properties of a Wall object. You can place doors in or against it by moving them with the cursor keys but they will not create a hole.

...but because there are all different shapes it takes so long to do.

Keeps you from the street [:)] I've spend hundreds of hours on some projects, not to mention the many hours creating custom models. It's a hobby, the point is that it takes time! And this is a large project with very few repeating layouts, so hardly any use for copy/paste.