If the business is already profitable having efficient cost structure, such improvements may go down in your priority list, but say in a turnaround case this is on top of the list.
One problem with many small (/manufacturing) businesses is lack of data. You will need to create systems (ERP/MRP....) to capture accurate data first for TDABC or ABC analysis or else, but that is expensive and time consuming of course. Meantime you can average out some expenses such as utility or direct labor per product to analyze cost structure / develop your pricing strategy, then excel together with your accounting system is the best.

Hi Eric, we often get engaged by buyers about 90 days after closing to do a full evaluation. Some of the more forward thinking individuals I have worked with will include us in the due diligence to get a better understanding of what they might change after closing and if there is fat they can get rid of.