Implementing grouping and layer assignment from the beginning is very important for the workflow. When I start a home, I immediately create my layers - Foundation, First Floor, Second Floor, Roof as the initial basics. Once I draw a particular floor (always draw on layer 0), I group it and assign it to the appropriate layer. Then you can draw on top of that layer to create the next group. Repeat the process and you will have a clean model with easy control.