Two hands are more than adequate, any more and there wouldn’t be room to work! Having the head fitted on a detachable block I find helps as one can fit plugs and the compression slows the descent of the block into the crankcase. I also put a sheet of cardboard or hardboard between the frame and the cylinder block to protect paintwork as the block is slid into position. Before I started using jubilee clips to hold the rings in position, I used to use a piece of cord attached to the head and wrapped a couple of times around the handlebars to lower the block in a reasonably controlled manner but since using jubilee clips I don’t find a need for the cord.
