Before we get into the nuts and bolts of the Honda 21-inch Variable Speed 4-in-1 Gas Walk Behind Self Propelled Lawn Mower we should point out that the model numbers HRX217VKA and HRX217K5VKA are used interchangeably by Honda to refer to this lawn mower and there do not appear to be any differences between the two. That said the best adjective to describe the HRX217VKA is powerful.
To sharpen them secure in a table vise. Now attach the blade sharpener to the end of your power drill. Make sure to wear eye protection and work gloves. Carefully use the sharpener to hone the cutting edges of your blades. Go slowly at first to get the feel of the best angle for meeting the blade and sharpener.
I know that many people prefer to hose their mowers down with a garden hose. I admit I have done it. Still doing that is risky. If water gets into the wiring air filter or engine you could really do some damage. Hand washing with damp rag is a drag but also your safest bet.