Came upon an interesting way of previewing buildings before you place them on the layout and what they may look like if you are doing some kitbashing. Take the parts of the building that you are in putting together, photocopy the four sides, cut these copies out and glue them onto scrap pieces of styrofoam. This way you have a good idea how the building will look at its proposed location, how much room it will take. If you do several up this way, as you build one you will still have a few of the photocopy ones near be so the area will not look too vacant.
For kitbashing, photocopy the parts that you wish to add or alter and do the adding/altering on the photocopies.
Have done a few design preservation building this way and looks good on the layout, fills up the spaces until the real one is built and detailed. With the photocopies glued to the styrofoam they are light and easily moved around to their best advantage. Just a thought. Ron..