Is there a hotkey for adding a block comment?

Yes, you can comment out several lines at once by selecting them and pressing Ctrl-/ (slash) (command-/ on a Mac). You can also use the comment package to comment out large sections of text. Just add

\usepackage{comment}

to your preamble, and then use

\begin{comment}
...
\end{comment}

in the text to create a block comment.

Another option is to enable vi editor mode and use the standard vi commands for commenting.