Activate the Smooth or Blur tool temporarily

`Shift`

All hotkeys for Autodesk Mudbox 2017 (Windows)

Camera and Plane Shortcuts Rotate the camera	`Alt` + `Drag`
Camera and Plane Shortcuts Track the camera	`Alt` + `Middle Drag`
Camera and Plane Shortcuts Dolly the camera	`Alt` + `Right Drag`
Camera and Plane Shortcuts Roll the camera	`Alt` + `Shift` + `Middle Drag`
Camera and Plane Shortcuts Focus on a location on the model	`F`
Camera and Plane Shortcuts Frame All	`A`
Camera and Plane Shortcuts Rotate an image plane	`E` + `Drag`
Camera and Plane Shortcuts Track/transform an image plane	`E` + `Middle Drag`
Camera and Plane Shortcuts Adjust the depth property for an image plane	`E` + `Right Drag`
Curve Create a curve	`Ctrl` + `C`
Curve End a Curve	`Enter`
Curve Rotate a curve	`C` + `Drag`
Curve Translate a curve	`C` + `Middle Drag`
Curve Scale a curve	`C` + `Right Drag`
Curve Hide All Curves	`Ctrl` + `H`
Curve Show All	`U`
Display Hide Selected	`H`
Display Hide All Curves	`Ctrl` + `H`
Display Show Selected	`Ctrl` + `U`
Display Show All	`U`
Display Flat Lighting	`Shift` + `L`
Display Wireframe	`W`
Display Show Both Sides	`Shift` + `B`
Display Light Direction	`L` + `Drag`
Display Full Screen	`Ctrl` + `T`
Display Expert Mode	`T`
Edit Menu Undo	`Ctrl` + `Z`
Edit Menu Redo	`Shift` + `Z`
Edit Menu Delete	`Delete`
Edit Menu Lock Mesh	`Shift` + `F`
Edit Menu Unlock Mesh	`Ctrl` + `Shift` + `F`
Edit Menu Freeze Selected	`Shift` + `M`
Edit Menu Invert Freeze	`Shift` + `I`
Edit Menu Unfreeze All	`Shift` + `U`
File Input and Output Create a new scene	`Ctrl` + `N`
File Input and Output Open a scene	`Ctrl` + `O`
File Input and Output Save current scene	`Ctrl` + `S`
File Input and Output Save Scene As	`Ctrl` + `Shift` + `S`
File Input and Output Export an image of the current 3D View as a paint layer to Photoshop (.psd)	`Alt` + `E`
File Input and Output Re-import a paint layer (image) of the 3D View updated in Photoshop.	`Alt` + `R`
File Input and Output Exit	`Ctrl` + `Q`
File Input and Output View Mudbox Help	`F1`
Image Browser Brighten or darken HDR image	`+` / `-`
Image Browser Reset HDR image	`0`
Image Browser View discrete color channels for an image	`1, 2, or 3`
Image Browser Zoom in and out on an image	`Ctrl` + `+` / `Ctrl` + `-`
Image Browser Pan around an image	`Alt` + `Drag`
Image Browser Next image	`Spacebar`
Image Browser Previous image	`Backspace`
Transformation Rotate the model	`X` + `Drag`
Transformation Track the model	`X` + `Middle Drag`
Transformation Scale the model	`X` + `Right Drag`
Sculpt and Paint Tool Adjust brush size	`B` + `Drag`
Sculpt and Paint Tool Adjust brush strength	`M` + `Drag`
Sculpt and Paint Tool Adjust color	`Ctrl` + `M`
Sculpt and Paint Tool Increase brush size in steps	`]`
Sculpt and Paint Tool Decrease brush size in steps	`[`
Sculpt and Paint Tool Increase brush strength in steps	`'`
Sculpt and Paint Tool Decrease brush strength in steps	`;`
Sculpt and Paint Tool Select tools from left to right on the current tool tray.	`0..9`
Sculpt and Paint Tool Invert Function	`Ctrl`
Sculpt and Paint Tool Activate the Smooth or Blur tool temporarily	`Shift`
Sculpt and Paint Tool Turn on the Smooth Values property temporarily to smooth color applied with Freeze or Mask.	`Shift`
Sculpt and Paint Tool Toggle Falloff	`Ctrl` + `\`
Sculpt and Paint Tool Mirror X	`Shift` + `Alt` + `X`
Sculpt and Paint Tool Mirror Y	`Shift` + `Alt` + `Y`
Sculpt and Paint Tool Mirror Z	`Shift` + `Alt` + `Z`
Sculpt and Paint Tool Sample color in the 3D View	`I`
Sculpt and Paint Tool Mirror Tangent	`Shift` + `Alt` + `T`
Sculpt and Paint Tool Mirror Off	`Shift` + `Alt` + `O`
Sculpt and Paint Tool Flatten to UV Space, Unflatten from UV Space	`Alt` + `T`
Selection Select All	`Ctrl` + `A`
Selection Invert Face Selection	`Ctrl` + `Shift` + `I`
Selection Deselect All	`Ctrl` + `D`
Selection Grow Selection	`Ctrl` + `]`
Selection Select Level	`Shift` + `A`
Selection Select Face	`Shift` + `S`
Selection Drag Rectangle	`Left Arrow+ Middle Drag`
Selection Select tools from left to right on the current tool tray.	`0..9`
Stencil Rotate	`S` + `Drag`
Stencil Translate	`S` + `Middle Drag`
Stencil Scale	`S` + `Right Drag`
Stencil Activate/Deactivate	`Q`
Subdivison and Symmetry Add Subdivision Level	`Shift` + `D`
Subdivison and Symmetry Step Level Up	`PgUp`
Subdivison and Symmetry Step Level Down	`PgDn`
Subdivison and Symmetry Set Topological Axis	`Ctrl` + `V`
Paint Layer Show/Hide Texture File	`Up Arrow`
Paint Layer Hide all texture tiles	`Ctrl` + `Down Arrow`
Paint Layer Show all texture tiles	`Ctrl` + `Up Arrow`
Paint Layer Composite paint strokes	`'`
Paint Layer Open Adjust Color window	`Ctrl` + `M`