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.
The Sun Joe MJ104E has more than 1250 five-star reviews on Amazon. Buyer Jim has had his Mow Joe for more than a year and left it in the weather and abused it otherwise. He is happy with how it has performed. He cautions against buying the 16-gauge extension cord recommended by Amazon. Instead choose 12 gauge for 100 feet or more and 14 gauge for under 100 feet.
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.