Keyboard Shortcut For Blur/Sharpen/Smudge

The tools nested under the Blur tool (Blur/sharpen/smudge) are the only set of tools in the tools panel without a keyboard shortcut.

You can however assign a shortcut to them by pressing Ctrl Alt Shift K (Mac: Command Opt Shift K) to open the Keyboard Shortcut editor. Choose “Tools” under the “Shortcuts for” drop-down and scroll-down to those tools and assign a letter to them.

Your best option for these is the letters K and N since they are available without having to change any other shortcuts.