98% of the total time it takes me to design something, usually involves deleting entire designs because they get a point where something is unfeasible, invalid geometry, or against all manufacturers' guidelines (will this shape work with a draft angle? etc.)

this is usually before i start adding intricacies such as shells, fillets, and other features, which do take a lot of effort, but making those by hand is more of the 'art' side of the process anyway

anything that gets me through the first 98% is welcome :)