I've been going down to central Florida at the end of March for many years. Parents winter on the St. Johns. Most seem to fish for crappie buy trolling close to the banks flipping jigs or bobber with minnow. My dad trolls a lot. Only time we might stay in one spot for a few minutes is if one of us catches one. But, most of the time is flip out , let it sink and raise up. We've had times this works great. But, is there a better way to fish?
Your dad is doing exactly what 95% do at that time of year. There is a ton of cover on the river and what is holding fish changes from day to day, hour to hour. Lots of places look very fishy but nobody home. Moving along and dipping everything in sight and some of the thickest, nastiest weed choked spots you could imagine. Find a good spot spend time till no more and move on again. Of course you could anchor up/tie up and float minners and wait for em to show if they do. Getting into some of the lakes in the area Dexter, George and Woodruff you could spiderrig or longline.