Eliminating shadows with shapes in Preview

I've read many answers on how to eliminate shadows from shapes in Preview. None of them worked for me. As a last ditch effort I tried: Selection Tools > rectangle selection > activate rectangle lasso over an empty section of document and expand it to size needed > Edit > Copy > with it still activated (blue dots and moving outline) move rectangle over to area you want to hide > adjust outline to your needs > Paste. Voila! Instant whiteout without drop shadow.