allways start with the fill port, if the drain comes out but not the fill you cant service it. since it is only a drain plug it limits the amount of cleaning/flushing you can do anyway. as previously stated, siphon out of the fill plug and forget about it! dont fix it til it breaks as i have been guilty of to many times to count. harbor freight siphon pump $7. oops, if i also misread your post, is it already drained? if so still use a siphon pump and drill out a old wine cork to allow the tube to pass through, install in the drain hole and put the prescribed amount of fluid in. then quickly! pull the cork and install the plug. i know it is a mess but you wont lose more than an ounce or two of fluid.