1) I use a different layer for each profile so that I can use Estimator’s Layers tab to assign costs based on attributes (like lineal footage) of that layer. For example, if I model a footing on a layer called FOOTING – I can then select the item, choose the attribute of FEET and add a cost per foot for labor. I may then ADD ASSOCIATED COST (+) and choose attribute of (YARD3 = CY) for the quantity of concrete. You can add as many additional costs as you like – you might use the FEET to calculate amount of rebar for the footing, etc.
2) The most important reason for it to be on Layers, is that once you have added these “typical” costs to a Layer and save it in your TEMPLATE file, then the next time you model a footing in a new job, your price is instantly provided in Estimator! You can edit the unit rates if need be, but it will save a lot of time for future models.