The next step in winterizing is to change the oil. You want to change the oil now to eliminate the dirt and to coat the engine with clean oil before storage. The steps are to run engine to warm up the oil so it flows better and to ensure that the dirt is suspended in the oil. Drain the oil. Remove oil filter and replace with a new one. Refill the engine with the recommended type and amount. Not much to it in telling but in practice? It could be that simple to a lot more complicated depending on what you are dealing with.
Lets start with 4 stroke outboards. Most will have a plug around the mid section ether on the side or on the back. Remove the plug and drain the oil. You may trim the motor and turn it to the side to allow for better draining. Once all the oil is drained reinstall the plug with a new gasket. Then remove and replace the filter making sure to lubricate the o-ring. Some outboards may require that the side cover be removed to access the filter. Finally refill with recommended oil checking the level with the dipstick periodically.
Changing oil on inboards or sterndrives can become a little more complicated mainly due to the construction of the boat. The oil needs to be extracted from the engine by pumping it out the dipstick or through a hose that is provided. After removing the oil remove the filter using the appropriate wrench. Be sure to have a catch pan below the filter or/and an oil absorbent cloth to prevent a mess in the bilge. Seats, bulkheads, or dividers might have to be removed to reach the filter unless you are lucky enough to have a remote filter. Install the correct filter making sure that you lubricate the o-ring. Refill the engine with the proper type and quantity of oil.
There you go, you now are ready to fog the engine.
Below are some recommended extractors and supplies.