Hi Colin,
As Maverick says, no need for buoys these days. To see the likely drift line I cut the motor somewhere near to but not over the wreck, and I turn on the Track function on my plotter. This traces the path of my boat onto the map; it looks like there's a line coming out of my boat showing where I've drifted. I use this to show me the drift angle that my boat will take when I'm over the wreck. Once I know the drift angle I can use this knowledge to position myself uptide of the wreck and start the first proper drift.
When you get a drift right, you can use the track line to simply motor back to the start of that drift track on your plotter and repeat.