Hey Lee
The way I did mine, was to only remove the rockers arms from the cylinder you are working on. You can see from the camshaft postion whether you are at TDC on compression. (i.e. both lobes facing down) So I don't think a whistle is necessary.
You can also see the piston with a torch to confirm it's at TDC.
btw Mine went from using almost 1 litre of oil per 1000km to using maybe 1-200ml between changes (5000km)
Hope you have similar results....................