Quick way to change case of the last word typed 

When you type a word and hit the spacebar, you can use the

Shift + F3 command to cycle through all Uppercase, all Lowercase, and Title (Sentence) case without first selecting the word. 

To change case of two or more words, hold down the Ctrl key and press the left arrow to select words, then press Shift + F3 to cycle through all Uppercase, all Lowercase, and Title case. 

Note:  If the word(s) selected are fully capitalized, Shift + F3 cycles through Lowercase first, Title case, then Uppercase. 

Remember:  You have the ability to reassign any built-in key assignment to keys that are not an awkward stretch for your fingers.