You can create your own custom keyboard shortcuts for Tools, Application, Panel Menus and Taskspaces in order to dramatically increase the speed at which you select commands. My rule of thumb is: if I use the feature/tool more than 3 times a day, then I’m going to either learn the shortcut assigned to it or, if there isn’t one, I’m going to assign my own.
To modify the shortcuts select Edit > Keyboard Shortcuts. The shortcuts for the Tools are limited to single letters so you will probably need to remove the shortcut for one tool in order to assign it to another (the letter “N” is the only letter unused by the default set). For example if you constantly toggle back and fourth between the Brush and Mixer Brush tools, you might want leave the Brush shortcut set to B while changing the Mixer Brush to “O” if you rarely use the Dodge/Burn/Sponge tools.
Shortcuts for Application and Panel Menus must contain the Command key (Mac) | Control key (Win) as a modifier or, an F-key. They may also contain the Shift key (for more variations).