I also drain mine completely 1st, in clouding the j tube. Blow out the heater and the pour in though one of the hoses at the thermostat housing and fill the heater via the upper hose. At no point do I run the engine, this all happens in the garage on whatever day I decide the season is done.
When you drain the block, make sure to jam a screwdriver in the block drains to make sure they are not clogged.