A wacker plate is only really used to compact sand on installation or when replacing blocks, you can use a rubber mallet and bit of wood to re-bed the blocks, otherwise just apply sand and re-brush.
The best way to get rid of a polyeurethane coating on driveways is to sand blast, and then use a re-curculating industrial vacuum extractor to save on mess, then let the driveway dry for two or three days to release the moisture (milky white stain), then apply a acrylic coating.