There is a drain hole on the side of the engine and this needs cleaing with a coat hanger wire etc. In any event, once the engine gets upto temp the heat should boil off any water in the plug galleries.
That just drains the plug recesses. There is no drain for the Coolant pipe area that I could see when checking the valves some time ago.
@Gnasher, is there any reason why owners could not coat the bottom of these pipe galleries with grease? As it would both protect the bottoms of the pipes and all the crap that goes in there would stick to the grease etc..