vi comment and uncomment multiple lines

Comment multiple lines

1. Press ESC
2. Go to the starting line, press ctrl+v to enable visual block mode
3. Use down arrow or k key to select multiple lines
4. Press shift+I to enable insert mode
5. Press # to add comment to first line, then press ESC, then wait for 1 second to get # added to all lines

Another option is:

1. Press ESC
2. Go to the starting line, press ctrl+v to enable visual block mode
3. Use down arrow or k key to select multiple lines
4. Press shift+ : to do search and replace ('<,'> will be automatically added)
5. Type  s/^/#/ to add # to comment out selected lines

Uncomment multiple lines

1. Press ctrl+v to enable visual block mode
2. Move down to select lines
3. Press x to uncomment selected lines