Another option for refilling is to buy some spare thermostat o-rings and refill from the thermostat housing. You don't need to detach any hoses, and filling the block goes quite a bit faster.

When the block is almost filled (or rather, the housing almost up to where the thermostat would sit, put the thermostat back in, re-attach the housing, and finish topping off from the overflow tank.

A little more work, a little less tedious.