I used a handheld GPS before my recent sonor unit that has it built in. If you don't have one, they are cheap on Facebook marketplace.
Without any GPS I would start slow and add speed until you "feel" the crankbait. From there the fish will tell you. It's difficult to say which setting because its constantly changing depending on the wind, waves, more or less weight in the boat, etc.
You'll get 'em!