Launching
Any ships chandler will sell you self sinking rope, and whilst it is strong I personally find it slips all too easily whilst lifting or carrying a hull. I found that (like Gregg suggested) using luggage straps (1" webbing) gives much better hold on the hull. I attach small pieces of lead to sink the straps and staple to broom handles to give a good safe lift.
BikerJohn
You have had several suggestions for launching/recovery slings. if your particular water does not have a firm launching edge then you may need to consider a wheeled cradle that you can push into the water to launch and recover.
Dave