All natural NZ bees wax for sealing your dowel holes after you have tapped the dowels in. This helps keep moisture in, and critters out, at the sites where the dowels have been insterted. Simply melt the wax in a double boiler and dab it on to the drill holes with an old paint brush or similar. Take note the brush will probably not be very good to use as a brush any more after that. 
 
APPROXIMATE AMOUNTS NEEDED
100 dowels = 100g beeswax