Kevin,
Yes, remove the tops for the cleaners and blow and plug each line. Then cover the units (The tops won't go back on with the lines plugged)
The only thing that comes to mind for the wedges is ladder/ handrail anchor cup freeze protection. Are they the right size and number for this?
For the heater, there should be a petcock or winterizing plug on the bottom of the manifold (where the pipes come in and out) which should be opened and left open. Also, most of the 'box shaped heaters' have a pressure switch which should be removed so that the water can drain from that line. It helps to blow some air through the heater lines once drains and pressure switch line are open.