if you're talking about a push mower, remember to tilt it with the carburetor up.

I use a 1.5 inch steel putty blade.

When I cut grass for work we used lots of various metal things, but nothing beat about a 3 inch stiff putty knife.

Putty knife is good. My Honda HRX is a easy one to keep clean with water.

Once a year, I remove my deck from the mower (riding mower). Flip it over and power wash it well. I then apply a coat of epoxy paint from a spray can. Just don't spray too much water directly into the spindles etc. when power washing. Otherwise, the bearings will go bad sooner due to moisture. My mower - a Scotts model L2048 is now 17 years old with 700 hours on it. I once replaced the spindle bearings. It has a 48 inch deck with three blades. I do the power washing at the end of the season, when it is ready for storage.