You should be aware that Google no longer has any involvement with either SketchUp or Layout, so referring to them as Google products is erroneous.
As requested, here are some LINKS to Layout materials and tutorial information.
Most of the modeling work should be performed directly in SketchUp and specific scenes developed in SU can then be exported into Layout either as 2D views or as perspective views. Typically the modifications performed in LO may consist of dimensioning or providing text labels. There may be occasions where you will edit materials or colors (in Layout), but for the most part the bulk of your work should be done in SU, even the minor editing, before you take the work to Layout. Just remember to update and save your LO files after making any edits to the corresponding SU model.