I think the only way to do it is to stack merit on merit, not on need based aid.
If the school determines your EFC is $20k, the school is going to expect you to contribute that $20k. It’s going to knock out all its aid before it touches that $20k. Knocking out loans and work study does benefit you, but that $20k is still going to be the number the school thinks you can contribute. If the COA is $40k, the school is going to think you can send in $20k. If the COA is $70k, the school is still going to think you can contribute $20k.